Auto TroubleShooter CP7677 OPERATING INSTRUCTIONS - Actron · PDF fileIgnition System Testing..... 19 - Ignition Coil Testing ..... 19 - Ignition System Wires ..... 21 - Hall Effect

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IndexSafety Precautions ......................................... 2

Vehicle Service Information ........................... 3

Visual Inspection ............................................ 3

Electrical Specifications ............................... 34

Warranty ..................................................... 104

1. Multimeter Basic Functions

Functions and Display Definitions ............ 4

Setting the Range ..................................... 6

Battery and Fuse Replacement ................ 7

Measuring DC Voltage .............................. 8

Measuring AC Voltage .............................. 8

Measuring Resistance .............................. 9

Measuring DC Current .............................. 9

Testing for Continuity .............................. 10

Testing Diodes ........................................ 11

Measuring Engine RPM .......................... 11

Measuring Dwell ..................................... 12

2. Automotive Testing with the CP7677

General Testing ...................................... 13- Testing Fuses ...................................... 13- Testing Switches ................................. 13- Testing Solenoids and Relays ............ 14

Starting / Charging System Testing ....... 15

- No Load Battery Test .......................... 15

- Engine Off Battery Current Draw ........ 15

CP7677Auto TroubleShooter™

OPERATINGINSTRUCTIONS

- Cranking Voltage/Battery Load Test ... 16

- Voltage Drops ...................................... 17

- Charging System Voltage Test ........... 18

Ignition System Testing .......................... 19

- Ignition Coil Testing ............................. 19

- Ignition System Wires .......................... 21

- Hall Effect Sensors/Switches .............. 22

- Magnetic Pick-Up Coils ....................... 23

- Reluctance Sensors ............................ 23

- Ignition Coil Switching Action .............. 24

Fuel System Testing ............................... 25

- Testing GM C-3 Mixture ControlSolenoid Dwell .................................... 25

- Measuring Fuel Injector Resistance ... 26

Testing Engine Sensors .......................... 27

- Oxygen (O2) Type Sensors ................. 27

- Temperature Type Sensors ................ 29

- Position Type Sensors –Throttle and EGR Valve Position,Vane Air Flow ...................................... 30

- Manifold Absolute Pressure (MAP) andBarometric Pressure (BARO) Sensors 31

- Mass Air Flow (MAF) Sensors ............ 32

Instrucciones en español ....35Instructions en français .......69

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SAFETY GUIDELINESTO PREVENT ACCIDENTS THAT COULD RESULT IN SERIOUS INJURY

AND/OR DAMAGE TO YOUR VEHICLE OR TEST EQUIPMENT,CAREFULLY FOLLOW THESE SAFETY RULES AND TEST PROCEDURES

• Always wear approved eye protection.

• Always operate the vehicle in a well ventilated area. Do not inhale exhaust gases– they are very poisonous!

• Always keep yourself, tools and test equipment away from all moving or hotengine parts.

• Always make sure the vehicle is in park (Automatic transmission) or neutral(manual transmission) and that the parking brake is firmly set. Block the drivewheels.

• Never lay tools on vehicle battery. You may short the terminals together causingharm to yourself, the tools or the battery.

• Never smoke or have open flames near vehicle. Vapors from gasoline andcharging battery are highly flammable and explosive.

• Never leave vehicle unattended while running tests.

• Always keep a fire extinguisher suitable for gasoline/electrical/chemical fireshandy.

• Always use extreme caution when working around the ignition coil, distributorcap, ignition wires, and spark plugs. These components contain High Voltagewhen the engine is running.

• Always turn ignition key OFF when connecting or disconnecting electricalcomponents, unless otherwise instructed.

• Always follow vehicle manufacturer’s warnings, cautions and service procedures.

CAUTION:Some vehicles are equipped with safety air bags. You must follow vehicle servicemanual cautions when working around the air bag components or wiring. If thecautions are not followed, the air bag may open up unexpectedly, resulting in personalinjury. Note that the air bag can still open up several minutes after the ignition key isoff (or even if the vehicle battery is disconnected) because of a special energy reservemodule.

All information, illustrations and specifications contained in this manual are based on the latestinformation available from industry sources at the time of publication. No warranty (expressedor implied) can be made for its accuracy or completeness, nor is any responsibility assumed byActron Manufacturing Co. or anyone connected with it for loss or damages suffered throughreliance on any information contained in this manual or misuse of accompanying product. ActronManufacturing Co. reserves the right to make changes at any time to this manual or accompa-nying product without obligation to notify any person or organization of such changes.

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Vehicle Service Manual – Sources For ServiceInformationThe following is a list of sources to obtain vehicle service information for your specificvehicle.

• Contact your local Automotive Dealership Parts Department.

• Contact local retail auto parts stores for aftermarket vehicle service information.

• Contact your local library. Libraries often allow you to check-out automotive servicemanuals.

Do a Thorough Visual InspectionDo a thorough visual and “hands-on” underhood inspection before starting anydiagnostic procedure! You can find the cause of many problems by just looking,thereby saving yourself a lot of time.

• Has the vehicle been servicedrecently? Sometimes things getreconnected in the wrong place, ornot at all.

• Don’t take shortcuts. Inspect hosesand wiring which may be difficult tosee due to location.

• Inspect the air cleaner andductwork for defects.

• Check sensors and actuators fordamage.

• Inspect ignition wires for:

- Damaged terminals.

- Split or cracked spark plug boots

- Splits, cuts or breaks in the ignitionwires and insulation.

• Inspect all vacuum hoses for:

- Correct routing. Refer to vehicleservice manual, or Vehicle Emis-sion Control Information(VECI)decal located in the engine com-partment.

- Pinches and kinks.

- Splits, cuts or breaks.

• Inspect wiring for:

- Contact with sharp edges.

- Contact with hot surfaces, such asexhaust manifolds.

- Pinched, burned or chafed insula-tion.

- Proper routing and connections.

• Check electrical connectors for:

- Corrosion on pins.

- Bent or damaged pins.

- Contacts not properly seated inhousing.

- Bad wire crimps to terminals.

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Alligator Clip AdaptersSome multimeter tests and measurements are more easily done usingalligator clips instead of test prods. For these tests, push the crimp end of thealligator clip onto the test prod. If the crimp on the alligator clip becomes loose,then remove the alligator clip from the test prod and re-crimp using a pair ofpliers.

Section 1. Multimeter Basic FunctionsDigital multimeters or DMMs have many special features and functions. This sectiondefines these features and functions, and explains how to use these functions to makevarious measurements.

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8

7

1

2

3

5

12

49

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Functions and Display Definitions

1. ROTARY SWITCHSwitch is rotated to select a function.

2. DC VOLTSThis function is used for measuring DC(Direct Current) Voltages in the rangeof 0 to 1000V.

3. OHMSThis function is used for measuring theresistance of a component in an elec-trical circuit in the range of 0.1Ω to20MΩ. (Ω is the electrical symbol forOhms)

4. DIODE CHECK / CONTINUITY TESTSThis function is used to check whether adiode is good or bad. It is also used forfast continuity checks of wires and ter-minals. An audible tone will sound if awire and terminal are good.

5. HOLDPress HOLD button to retain data ondisplay. In the hold mode, the "H" an-nunciator is displayed.

6. TEST LEAD JACKSBLACK Test Lead is al-ways inserted in the COMjack.

RED Test Lead is in-serted in the jack corre-sponding to the multim-eter rotary switch setting.

8. DC AMPSThis function is used for measuring DC(Direct Current) Amps in the range of 0to 10A.

9. DWELLThis function is used for measuringDWELL on distributor ignition systems,and solenoids.

10. TACHThis function is used for measuringengine speed (RPM).

11. ON/OFF

Press to turn power ON. Press again toturn power OFF.

12. DISPLAYUsed to display all measurements andmultimeter information.

Low Battery – If this symbol appearsin the lower left corner of the display,

then replace the inter-nal 9V battery. (SeeFuse and Battery re-placement on page 7.)

Overrange Indication– If “1” or “-1” appearson the left side of thedisplay, then the multi-meter is set to a rangethat is too small for thepresent measurementbeing taken. Increasethe range until this dis-appears. If it does not

disappear after all the ranges for aparticular function have been tried, thenthe value being measured is too largefor the multimeter to measure. (SeeSetting the Range on page 6.)

Zero AdjustmentThe multimeter will automatically zero onthe Volts, Amps and RPM functions.

Automatic Polarity SensingThe multimeter display will show a minus (-)sign on the DC Volts and DC Amps functionswhen test lead hook-up is reversed.

Always connect TEST LEADS to the mul-timeter before connecting them to thecircuit under test!!

7. AC VOLTSThis function is used for measuring ACVoltages in the range of 0 to 750V.

DC VOLTSAC VOLTS

DIODESCONTINUITY

RPMDWELLOHMS

DC AMPS

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Setting the RangeTwo of the most commonly asked ques-tions about digital multimeters are Whatdoes Range mean? and How do I knowwhat Range the multimeter should beset to?

What Does Range mean?

Range refers to the largest value themultimeter can measure with the rotaryswitch in that position. If the multimeteris set to the 20V DC range, then thehighest voltage the multimeter can mea-sure is 20V in that range.

EXAMPLE: Measuring Vehicle BatteryVoltage (See Fig. 1)

Now assume we set the multimeter tothe 2V range. (See Fig. 2)

The multimeter display now shows a “1”and nothing else. This means the multi-meter is being overranged or in otherwords the value being measured is largerthan the current range. The range shouldbe increased until a value is shown onthe display. If you are in the highestrange and the multimeter is still showingthat it is overranging, then the valuebeing measured is too large for the mul-timeter to measure.

How do I know what Range the multi-meter should be set to?

The multimeter should be set in thelowest possible range withoutoverranging.

EXAMPLE: Measuring an unknown re-sistance

Let’s assume the multimeter is con-nected to an engine coolant sensor withunknown resistance. (See Fig. 3)

Fig. 2

Fig. 1

Let’s assume the multimeter is con-nected to the battery and set to the 20Vrange.

The display reads 12.56. This meansthere is 12.56V across the battery termi-nals.

Fig. 3

Start by setting the multimeter to thelargest OHM range. The display reads0.0Ω or a short circuit.

This sensor can’t be shorted so reducethe range setting until you get a value ofresistance.

At the 200KΩ range the multimeter mea-sured a value of 4.0. This means there is4KΩ of resistance across the enginecoolant sensor terminals. (See Fig. 4)

If we change the multimeter to the 20KΩrange (See Fig. 5) the display shows a

Red

Black

Red

Black

BlackRed

7

Fig. 4

Fig. 5value of3.87KΩ . Theactual value ofresistance is3.87KΩ and not4KΩ that wasmeasured inthe 200KΩrange. This isvery importantbecause if themanufacturerspecificationssay that thesensor shouldread 3.8-3.9KΩat 70°F then onthe 200KΩrange the sensor would be defective, butat the 20KΩ range it would test good.

Now set the multimeter to the 2KΩ range.(See Fig. 6) Thedisplay will indi-cate anoverrange con-dition because3.87KΩ is largerthan 2KΩ.

This exampleshows that bydecreasing therange you in-crease the ac-curacy of yourmeasurement.When youchange therange, youchange the lo-cation of the decimal point. This changes

Fig. 6

the accuracy of the measurement by ei-ther increasing or decreasing the numberof digits after the decimal point.

Battery and FuseReplacementImportant: A 9 Volt battery must be in-stalled before using the digital multim-eter. (see procedure below for installa-tion)

Battery Replacement

1. Turn multimeter OFF.

2. Remove test leads frommultimeter.

3. Remove screw from batterycover.

4. Remove battery cover.

5. Install a new 9 Volt battery.

6. Re-assemble multimeter.

Fuse Replacement

1. Turn multimeter OFF.

2. Remove test leads frommultimeter.

3. Remove rubber holster.

4. Remove screw from batterycover, battery cover, and battery.

5. Remove screws from back ofmultimeter.

6. Remove back cover.

7. Remove fuse.

8. Replace fuse with same size andtype as originally installed.Use a 1/4" x 1-1/4", 10A, 250V, fastacting fuse or a 5mm x 20mm315mA, 250V fast acting fuse.

9. Re-assemble multimeter.

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Measuring DC VoltageThis multimeter can be used to measureDC voltages in the range from 0 to 1000V.You can use this multimeter to do any DCvoltage measurement called out in thevehicle service manual. The most com-mon applications are measuring voltagedrops, and checking if the correct voltagearrived at a sensor or a particular circuit.

To measure DC Voltages (see Fig. 7):

6. View reading on display - Noterange setting for correct units.

NOTE: 200mV = 0.2V

Measuring AC VoltageThis multimeter can be used to measureAC voltages in the range from 0 to 750V.

To measure AC Voltages (see Fig. 8):

Fig. 7

1. Insert BLACK test lead into COMtest lead jack.

2. Insert RED test lead into test lead jack.

3. Connect RED test lead to positive(+) side of voltage source.

4. Connect BLACK test lead to nega-tive (-) side of voltage source.

NOTE: If you don’t know which sideis positive (+) and which side is nega-tive (-), then arbitrarily connect theRED test lead to one side and theBLACK to the other. The multimeterautomatically senses polarity and willdisplay a minus (-) sign when nega-tive polarity is measured. If youswitch the RED and BLACK testleads, positive polarity will now beindicated on the display. Measuringnegative voltages causes no harmto the multimeter.

5. Turn multimeter rotary switch todesired voltage range.

If the approximate voltage is unknown,start at the largest voltage range anddecrease to the appropriate range asrequired. (See Setting the Range onpage 6)



3. Connect RED test lead to one sideof voltage source.

4. Connect BLACK test lead to otherside of voltage source.

5. Turn multimeter rotary switch todesired voltage range.

If the approximate voltage is un-known, start at the largest voltagerange and decrease to the appropri-ate range as required. (See Settingthe Range on page 6)


NOTE: 200mV = 0.2V

RedBlack

Fig. 8

Red

Black

9

Fig. 9

ments, polarity is not important. Thetest leads just have to be connectedacross the component.

6. Turn multimeter rotary switch todesired OHM range.

If the approximate resistance is un-known, start at the largest OHMrange and decrease to the appropri-ate range as required. (See Settingthe Range on page 6)


NOTE: 2KΩ = 2,000Ω; 2MΩ =2,000,000Ω

If you want to make precise resis-tance measurements, then subtractthe test lead resistance found in Step4 above from the display reading inStep 7. It is a good idea to do this forresistance measurements less than10Ω.

Measuring DC CurrentThis multimeter can be used to measureDC current in the range from 0 to 10A. Ifthe current you are measuring exceeds10A, the internal fuse will blow (see FuseReplacement on page 7). Unlike voltageand resistance measurements where themultimeter is connected across the com-ponent you are testing, current measure-ments must be made with the multimeterin series with the component. Isolatingcurrent drains and short circuits are someDC Current applications.

To measure DC Current (see Figs. 10 &11):


2. Insert RED test lead into "10A"test lead jack or "mA" test leadjack.

3. Disconnect or electrically open cir-cuit where you want to measurecurrent.

This is done by:

• Disconnecting wiring harness.

• Disconnecting wire from screw-ontype terminal.

• Unsolder lead from component if

Red Black

UnknownResistance

Measuring ResistanceResistance is measured in electricalunits called ohms (Ω). The digital multi-meter can measure resistance from 0.1Ωto 20MΩ or (20,000,000 ohms). Infiniteresistance is shown with a “1” on the leftside of display (See Setting the Rangeon page 6). You can use this multimeterto do any resistance measurement calledout in the vehicle service manual. Test-ing ignition coils, spark plug wires, andsome engine sensors are common usesfor the OHMS (Ω) function.

To measure Resistance (see Fig. 9):

1. Turn circuit power OFF.

To get an accurate resistance mea-surement and avoid possible damageto the digital multimeter and electricalcircuit under test, turn off all electricalpower in the circuit where the resis-tance measurement is being taken.



4. Turn multimeter rotary switch to200Ω range.

Touch RED and BLACK multimeterleads together and view reading ondisplay.

Display should read typically 0.2Ω to1.5Ω.

If display reading was greater than1.5Ω, check both ends of test leadsfor bad connections. If bad connec-tions are found, replace test leads.

5. Connect RED and BLACK testleads across component whereyou want to measure resistance.

When making resistance measure-

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working on printed circuit boards.

• Cut wire if there is no other pos-sible way to open electrical circuit.

4. Connect RED test lead to one sideof disconnected circuit.

5. Connect BLACK test lead to re-maining side of disconnected cir-cuit.

6. Turn multimeter rotary switch to10A DC position, or 200mA posi-tion.

7. View reading on display.

If minus (-) sign appears on display,then reverse RED and BLACK testleads.

Testing for ContinuityContinuity is a quick way to do a resis-tance test to determine if a circuit isopen or closed. The multimeter will beepwhen the circuit is closed or shorted, soyou don’t have to look at the display.Continuity checks are usually done whenchecking for blown fuses, switch opera-tion, and open or shorted wires.

To measure Continuity (see Fig. 12):

Fig. 12

Black

Red

Fig. 10

Black

Red

ElectricalDevice

DCVoltageSource

Fig. 11

Black

Red

ElectricalDevice

DCVoltageSource



3. Turn multimeter rotary switch to function.

4. Touch RED and BLACK test leadstogether to test continuity.

Listen for tone to verify proper op-eration.

5. Connect RED and BLACK testleads across component whereyou want to check for continuity.

Listen for tone:

• If you hear tone – Circuit is closedor shorted.

• If you don’t hear tone – Circuit isopen.

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Fig. 13

7. Switch RED and BLACK test leadsand repeat Step 6.

8. Test Results

If the display showed:

• A voltage drop of 0 volts in bothdirections, then the diode is shortedand needs to be replaced.

• A “1” appears in both directions,then the diode is an open circuitand needs to be replaced.

• The diode is good if the displayreads around 0.5V–0.7V in one di-rection and a “1” appears in theother direction indicating the multi-meter is overranged.

Measuring Engine RPMRPM refers to revolutions per minute.When using this function you must multi-ply the display reading by 10 to get actualRPM. If display reads 200 and the multim-eter is set to 6 cylinder RPM, the actualengine RPM is 10 times 200 or 2000 RPM.

To measure Engine RPM (see Fig. 14):

Testing DiodesA diode is an electrical component thatallows current to only flow in one direc-tion. When a positive voltage, generallygreater than 0.7V, is applied to the an-ode of a diode, the diode will turn on andallow current to flow. If this same volt-age is applied to the cathode, the diodewould remain off and no current wouldflow. Therefore, in order to test a diode,you must check it in both directions (i.e.anode-to-cathode, and cathode-to-an-ode). Diodes are typically found in alter-nators on automobiles.

Performing Diode Test (see Fig. 13):

TypicalIgnition

Coil

Ground

Black

Red

Fig. 14

Anode Cathode

Black

Red



3. Connect RED test lead to TACH(RPM) signal wire.

• If vehicle is DIS (DistributorlessIgnition System), then connect REDtest lead to the TACH signal wiregoing from the DIS module to thevehicle engine computer. (refer tovehicle service manual for locationof this wire)

• For all vehicles with distributors,





Check display – should reset to 0.00.

5. Disconnect one end of diode fromcircuit.

Diode must be totally isolated fromcircuit in order to test its functional-ity.

6. Connect RED and BLACK testleads across diode and view dis-play.

Display will show one of three things:

• A typical voltage drop of around0.7V.

• A voltage drop of 0 volts.

• A “1” will appear indicating the mul-timeter is overranged.

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connect RED test lead to negativeside of primary ignition coil. (referto vehicle service manual for loca-tion of ignition coil)

4. Connect BLACK test lead to a goodvehicle ground.

5. Turn multimeter rotary switch tocorrect CYLINDER selection.

6. Measure engine RPM while engineis cranking or running.


• Remember to multiply display read-ing by 10 to get actual RPM.

If display reads 200, then actual en-gine RPM is 10 times 200 or 2000RPM.

Measuring DwellDwell measuring was extremely impor-tant on breaker point ignition systems ofthe past. It referred to the length of time,in degrees, that the breaker points re-mained closed, while the camshaft wasrotating. Today’s vehicles use electronicignition and dwell is no longer adjust-able. Another application for dwell is intesting the mixture control solenoid onGM feedback carburetors.

To measure Dwell (see Fig. 15):

Ground

Black

Red

Fig. 15TypicalIgnition

Coil



3. Connect RED test lead to DWELLsignal wire.

• If measuring DWELL on breakerpoint ignition systems, connectRED test lead to negative side ofprimary ignition coil. (refer to ve-hicle service manual for location ofignition coil)

• If measuring DWELL on GM mix-ture control solenoids, connectRED test lead to ground side orcomputer driven side of solenoid.(refer to vehicle service manual forsolenoid location)

• If measuring DWELL on any arbi-trary ON/OFF device, connect REDtest lead to side of device that isbeing switched ON/OFF.


5. Turn multimeter rotary switch tocorrect DWELL CYLINDER posi-tion.


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Section 2. Automotive Testing

The digital multimeter is a very usefultool for trouble-shooting automotive elec-trical systems. This section describeshow to use the digital multimeter to testthe starting and charging system, igni-tion system, fuel system, and enginesensors. The digital multimeter can alsobe used for general testing of fuses,switches, solenoids, and relays.

General TestingThe digital multimeter can be used totest fuses, switches, solenoids, and re-lays.

Testing FusesThis test checks to see if a fuse is blown.You can use this test to check the internalfuses inside the digital multimeter.

To test Fuses (see Fig. 16):

• If you hear tone - Fuse is good.

• If you don’t hear tone - Fuse isblown and needs to be replaced.

NOTE: Always replace blown fuseswith same type and rating.

Testing SwitchesThis test checks to see if a switch“Opens” and “Closes” properly.

To test Switches (see Fig. 17):

Fig. 17

Red

Typical "Push"Button Switch






5. Connect BLACK test lead to oneside of switch.

6. Connect RED test lead to otherside of switch.

Listen for tone:

• If you hear tone - The switch isclosed.

• If you don’t hear tone - The switchis open.

7. Operate switch.

Listen for tone:






5. Connect RED and BLACK testleads to opposite ends of fuse.

Listen for tone:

Fig. 16

Red Black

Fuse

Black

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• If you hear tone - The switch isclosed.

• If you don’t hear tone - The switchis open.

8. Repeat Step 7 to verify switch op-eration.

Good Switch: Tone turns ON andOFF as you operate switch.

Bad Switch: Tone always ON or tonealways OFF as you operate switch.

4. Connect BLACK test lead to oneside of coil.

5. Connect RED test lead to otherside of coil.


• Typical solenoid / relay coil resis-tances are 200Ω or less.

• Refer to vehicle service manual foryour vehicles resistance range.

7. Test Results

Good Solenoid / Relay Coil: Displayin Step 6 is within manufacturersspecification.

Bad Solenoid / Relay Coil:

• Display in Step 6 is not within manu-facturers specifications.

• Display reads overrange on everyohms range indicating an open cir-cuit.

NOTE: Some relays and solenoidshave a diode placed across the coil.To test this diode see Testing Di-odes on page 11.



3. Turn multimeter rotary switch to200Ω function.

Most solenoids and relay coil resis-tances are less than 200Ω. If meteroverranges, turn multimeter rotaryswitch to next higher range. (seeSetting the Range on page 6)

This test checks to see if a solenoid orrelay have a broken coil. If the coil testsgood, it is still possible that the relay orsolenoid are defective. The relay canhave contacts that are welded or worndown, and the solenoid may stick whenthe coil is energized. This test does notcheck for those potential problems.

To test Solenoids and Relays (see Fig.18):

Relay orSolenoid

Red Black

Fig. 18

Testing Solenoids and Relays

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Starting/Charging System TestingThe starting system “turns over” the engine. It consists of the battery, starter motor,starter solenoid and/or relay, and associated wiring and connections. The chargingsystem keeps the battery charged when the engine is running. This system consistsof the alternator, voltage regulator, battery, and associated wiring and connections.The digital multimeter is a useful tool for checking the operation of these systems.

No Load Battery TestBefore you do any starting/charging sys-tem checks, you must first test the bat-tery to make sure it is fully charged.

Test Procedure (see Fig. 19):

Fig. 19

Black

Red

1. Turn Ignition Key OFF.

2. Turn ON headlights for 10 sec-onds to dissipate battery surfacecharge.



5. Disconnect positive (+) batterycable.

6. Connect RED test lead to positive(+) terminal of battery.

7. Connect BLACK test lead to nega-tive (-) terminal of battery.

8. Turn multimeter rotary switch to20V DC range.


10. Test Results.

Compare display reading in Step 9with the following chart.

PercentVoltage Battery is Charged

12.60Vor greater 100%

12.45V 75%

12.30V 50%

12.15V 25%

If battery is not 100% charged, thencharge it before doing anymore starting/charging system tests.

Engine Off BatteryCurrent DrawThis test measures the amount of cur-rent being drawn from the battery whenthe ignition key and engine are both off.This test helps to identify possiblesources of excessive battery currentdrain, which could eventually lead to a“dead” battery.

1. Turn Ignition Key and all accesso-ries OFF.

Make sure trunk, hood, and domelights are all OFF.

(See Fig. 20)


3. Insert RED test lead into "A" (or"mA") test lead jack.

Black Red

Fig. 20

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4. Disconnect positive (+) batterycable.

5. Connect RED test lead to positive(+) battery terminal.

6. Connect BLACK test lead to posi-tive (+) battery cable.

NOTE: Do not start vehicle during thistest, because multimeter damage mayresult.

7. Turn multimeter rotary switch to10A DC (or 200 mA) position.


• Typical current draw is 100mA.(1mA = 0.001A)

• Refer to vehicle service manual formanufacturers specific Engine OffBattery Current Draw.

NOTE: Radio station presets andclocks are accounted for in the 100mAtypical current draw.

9. Test Results.

Normal Current Draw: Display read-ing in Step 8 is within manufacturersspecifications.

Excessive Current Draw:

- Display reading in Step 8 is well out-side manufacturers specifications.

- Remove Fuses from fuse box oneat a time until source of excessivecurrent draw is located.

- Non-Fused circuits such as head-lights, relays, and solenoids shouldalso be checked as possible cur-rent drains on battery.

- When source of excessive currentdrain is found, service as necessary.

Cranking Voltage -Battery Load TestThis test checks the battery to see if it isdelivering enough voltage to the startermotor under cranking conditions.


1. Disable ignition system so vehiclewon’t start.

Disconnect the primary of the igni-tion coil or the distributor pick-up coil

or the cam/crank sensor to disablethe ignition system. Refer to vehicleservice manual for disabling proce-dure.






7. Crank engine for 15 seconds con-tinuously while observing display.

8. Test Results.

Compare display reading in Step 7with chart below.

Voltage Temperature

9.6V or greater 70 °F and Above

9.5V 60 °F

9.4V 50 °F

9.3V 40 °F

9.1V 30 °F

8.9V 20 °F

8.7V 10 °F

8.5V 0 °F

If voltage on display corresponds toabove voltage vs. temperature chart,then cranking system is normal.

If voltage on display does not corre-spond to chart, then it is possible thatthe battery, battery cables, starting sys-tem cables, starter solenoid, or startermotor are defective.

Fig. 21

Red Black

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If multimeter overranges, turn multim-eter rotary switch to the 2V DC range.(See Setting the Range on page 6)

6. Crank engine until steady readingis on display.

• Record results at each point asdisplayed on multimeter.

• Repeat Step 4 & 5 until all pointsare checked.

7. Test Results –

Estimated Voltage Drop of StarterCircuit Components

Component Voltage

Switches 300mV

Wire or Cable 200mV

Ground 100mV

Battery CableConnectors 50mV

Connections 0.0V

• Compare voltage readings in Step6 with above chart.

• If any voltages read high, inspect com-ponent and connection for defects.

• If defects are found, service asnecessary.

Voltage DropsThis test measures the voltage drop acrosswires, switches, cables, solenoids, andconnections. With this test you can findexcessive resistance in the starter sys-tem. This resistance restricts the amountof current that reaches the starter motorresulting in low battery load voltage and aslow cranking engine at starting.


1. Disable ignition system so vehiclewon’t start.

Disconnect the primary of the igni-tion coil or the distributor pick-up coilor the cam/crank sensor to disablethe ignition system. Refer to vehicleservice manual for disabling proce-dure.



4. Connect test leads.

Refer to Typical Cranking VoltageLoss Circuit (Fig. 22).

• Connect RED and BLACK test leadsalternately between 1 & 2, 2 & 3, 4 &5, 5 & 6, 6 & 7, 7 & 9, 8 & 9, and 8 &10.

5. Turn multimeter rotary switch to200mV DC range.

110

24

5

6 8

7

7

9

896

2

4

5

3

3

Red Black

Fig. 22 Typical Cranking VoltageLoss Circuit

SolenoidThis is a representative sample ofone type of cranking circuit. Yourvehicle may use a different circuitwith different components orlocations. Consult your vehicleservice manual.

Starter

18

8. Open throttle and Hold enginespeed (RPM) between 1800 and2800 RPM.

Hold this speed through Step 11 -Have an assistance help hold speed.


Voltage reading should not changefrom Step 7 by more than 0.5V.

10. Load the electrical system by turn-ing on the lights, windshield wip-ers, and setting the blower fan onhigh.


Voltage should not drop down belowabout 13.0V.

12. Shut off all accessories, returnengine to curb idle and shut off.

13. Test Results.

• If voltage readings in Steps 7, 9,and 11 were as expected, thencharging system is normal.

• If any voltage readings in Steps 7,9, and 11 were different then shownhere or in vehicle service manual,then check for a loose alternatorbelt, defective regulator or alterna-tor, poor connections, or open al-ternator field current.

• Refer to vehicle service manual forfurther diagnosis.

This test checks the charging system tosee if it charges the battery and pro-vides power to the rest of the vehicleselectrical systems (lights, fan, radio etc).


Fig. 23

Red Black






6. Start engine - Let idle.

7. Turn off all accessories and viewreading on display.

• Charging system is normal if dis-play reads 13.2 to 15.2 volts.

• If display voltage is not between13.2 to 15.2 volts, then proceed toStep 13.

Charging System Voltage Test

19

Ignition System TestingThe ignition system is responsible for providing the spark that ignites the fuel in the cylinder.Ignition system components that the digital multimeter can test are the primary andsecondary ignition coil resistance, spark plug wire resistance, hall effect switches/sensors,reluctance pick-up coil sensors, and the switching action of the primary ignition coil.

Ignition Coil TestingThis test measures the resistance of theprimary and secondary of an ignitioncoi l . This test can be used fordistributorless ignition systems (DIS)provided the primary and secondary ig-nition coil terminals are easily acces-sible.

Test Procedure:

1. If engine is HOT let it COOL downbefore proceeding.

2. Disconnect ignition coil from ig-nition system.

3. Insert BLACK test lead into COMtest lead jack (see Fig. 24).

7. Connect test leads.

• Connect RED test lead to primaryignition coil positive (+) terminal.

• Connect BLACK test lead to primaryignition coil negative (-) terminal.

• Refer to vehicle service manual forlocation of primary ignition coil ter-minals.


Subtract test lead resistance foundin Step 6 from above reading.

9. If vehicle is DIS, repeat Steps 7and 8 for remaining ignition coils.

Typical CylindricalIgnition Coil

BlackRed

PrimaryCoil

SecondaryCoil

Fig. 25

Typical CylindricalIgnition Coil

Black

SecondaryCoil

PrimaryCoil

Red

4. Insert RED testlead into

testlead jack.

5. Turn multimeterrotary switch to200Ω range.

6. Touch RED andBLACK multim-eter leads to-gether and viewreading on dis-play.

10. Test Results - Pri-mary Coil

• Typical resistancerange of primaryignition coils is 0.3- 2.0Ω.

• Refer to vehicleservice manualfor your vehiclesresistance range.

11. Turn multimeterrotary switch to200KΩ range (seeFig. 25).

Fig. 24

20

12. Move RED test lead to secondaryignition coil terminal.

• Refer to vehicle service manual forlocation of secondary ignition coilterminal.

• Verify BLACK test lead is con-nected to primary ignition coil nega-tive (-) terminal.


14. If vehicle is DIS, repeat Steps 12and 13 for remaining ignition coils.

15. Test Results - Secondary Coil

• Typical resistance range of sec-ondary ignition coils is 6.0 - 30.0KΩ.


16. Repeat test procedure for a HOTignition coil.

NOTE: It is a good idea to testignition coils when they are both hotand cold, because the resistance ofthe coil could change with tempera-ture. This will also help in diagnosingintermittent ignition system prob-lems.

17. Test Results - Overall

Good Ignition Coil: Resistance read-ings in Steps 10, 15 and 16 werewithin manufacturers specification.

Bad Ignition Coil: Resistance read-ings in Steps 10, 15 and 16 are notwithin manufacturers specification.

21

Ignition System Wires

This test measures the resistanceof spark plug and coil tower wireswhile they are being flexed. Thistest can be used for distributorlessignition systems (DIS) provided thesystem does not mount the ignitioncoil directly on the spark plug.

Test Procedure:

1. Remove ignition system wiresone at a time from engine.

• Always grasp ignition systemwires on the boot when re-moving.

• Twist the boots about a half turnwhile pulling gently to remove them.

• Refer to vehicle service manual forignition wire removal procedure.

• Inspect ignition wires for cracks,chaffed insulation, and corrodedends.

NOTE: Some Chrysler products usea “positive-locking” terminal electrodespark plug wire. These wires canonly be removed from inside the dis-tributor cap. Damage may result ifother means of removal are at-tempted. Refer to vehicle servicemanual for procedure.

NOTE: Some spark plug wires havesheet metal jackets with the follow-ing symbol: . This type of plugwire contains an “air gap” resistorand can only be checked with anoscilloscope.

2. Insert BLACK test lead into COMtest lead jack (see Fig. 26).


4. Connect RED test lead to one endof ignition wire and BLACK testlead to other end.

5. Turn multimeter rotary switch to200KΩ range.

6. View reading on display while flex-ing ignition wire and boot in sev-eral places.

• Typical resistance range is 3KΩ to50KΩ or approximately 10KΩ perfoot of wire.

• Refer to vehicle service manualfor your vehicles resistance range.

• As you flex ignition wire, the dis-play should remain steady.

7. Test Results

Good Ignition Wire: Display readingis within manufacturers specifica-tion and remains steady while wireis flexed.

Bad Ignition Wire: Display readingerratically changes as ignition wireis flexed or display reading is notwithin manufacturers specification.

Fig. 26

Black

Spark Plug Wire

Red

22

9V

Hall Effect sensors are used wheneverthe vehicle computer needs to knowspeed and position of a rotating object.Hall Effect sensors are commonly usedin ignition systems to determine cam-shaft and crankshaft position so the ve-hicle computer knows the optimum timeto fire the ignition coil(s) and turn on thefuel injectors. This test checks for properoperation of the Hall Effect sensor /switch.


1. Remove Hall Effect Sensor fromvehicle.

Refer to vehicle service manual forprocedure.

2. Connect 9V battery to sensorPOWER and GROUND pins.

• Connect positive(+) terminal of 9Vbattery to sensor POWER pin.

• Connect negative(-) terminal of 9Vbattery to sensor GROUND pin.

• Refer to illustrations for POWERand GROUND pin locations.

• For sensors not illustrated refer tovehicle service manual for pin lo-cations.



5. Connect RED test lead to sensorSIGNAL pin.

6. Connect BLACK test lead to 9Vbattery negative(-) pin.


Multimeter should sound a tone.

8. Slide a flat blade of iron or mag-netic steel between sensor andmagnet. (Use a scrap of sheet metal,knife blade, steel ruler, etc.)

• Multimeter tone should stop anddisplay should overrange.

• Remove steel blade and multim-eter should again sound a tone.

• It is O.K. if display changes errati-cally after metal blade is removed.

• Repeat several times to verify re-sults.

9. Test Results

Good Sensor: Multimeter togglesfrom tone to overrange as steel bladeis inserted and removed.

Bad Sensor: No change in multim-eter as steel blade is inserted andremoved.

Fig. 27

Red

POWER

SIGNAL

SIGNALPOWER

GROUND SIGNAL

Sensor

GROUND

JumperWires

Black POWER

Magnet

Iron or SteelBlade

Chrysler DistributorHall Effect

Ford DistributorHall Effect

Typical HallEffect Sensor

GROUND

Hall Effect Sensors/Switches

23

Magnetic Pick-Up Coils – Reluctance Sensors

Reluctance sensors are used wheneverthe vehicle computer needs to knowspeed and position of a rotating object.Reluctance sensors are commonly usedin ignition systems to determine cam-shaft and crankshaft position so the ve-hicle computer knows the optimum timeto fire the ignition coil(s) and turn on thefuel injectors. This test checks the reluc-tance sensor for an open or shorted coil.This test does not check the air gap orvoltage output of the sensor.


ReluctanceSensor

Red

Black



ReluctorRing

Magnet

3. Connect RED test lead to eithersensor pin.

4. Connect BLACK test lead to re-maining sensor pin.


6. View reading on display while flex-ing sensor wires in several places.

• Typical resistance range is 150 -1000Ω.


• As you flex sensorwires, the displayshould remain steady.

7. Test Results

Good Sensor: Displayreading is within manu-facturers specificationand remains steadywhile sensor wires areflexed.

Bad Sensor: Displayreading errat ical lychanges as sensor wiresare flexed or displayreading is not withinmanufacturers specifi-cation.

Fig. 28

24

Ignition Coil Switching Action

This test checks to see if the negativeterminal of the primary ignition coil isgetting switched ON and OFF via theignition module and camshaft / crank-shaft position sensors. This switchingaction is where the RPM or tach signaloriginates. This test is primarily used fora no start condition.


Fig. 29TypicalIgnition

Coil

Ground

Black

Red



3. Connect RED test lead to TACHsignal wire.

• If vehicle is DIS (DistributorlessIgnition System), then connect REDtest lead to the TACH signal wiregoing from the DIS module to thevehicle engine computer. (refer to

vehicle service manual for locationof this wire)

• For all vehicles with distributors,connect RED test lead to negativeside of primary ignition coil. (referto vehicle service manual for loca-tion of ignition coil)


5. Turn multimeter rotary switchto correct CYLINDER selec-tion in RPM.

6. View reading on display whileengine is cranking.

• Typical cranking RPM rangeis 50-275 RPM depending ontemperature, size of engine,and battery condition.

• Refer to vehicle servicemanual for specific vehiclecranking RPM range.

7. Test Results.

Good Coil Switching Action: Displayreading indicated a value consistentwith manufacturers specifications.

Bad Coil Switching Action:

• Display read zero RPM, meaningthe ignition coil is not beingswitched ON and OFF.

• Check ignition system for wiringdefects, and test the camshaft andcrankshaft sensors.

25

Fuel System TestingThe requirements for lower vehicle emissionshas increased the need for more precise enginefuel control. Auto manufacturers began usingelectronically controlled carburetors in 1980 tomeet emission requirements. Today’s modernvehicles use electronic fuel injection to preciselycontrol fuel and further lower emissions. Thedigital multimeter can be used to test the fuelmixture control solenoid on Gen-eral Motors vehicles and to mea-sure fuel injector resistance.

Testing GM C-3 Mixture Control Solenoid Dwell

This solenoid is located in the carbure-tor. Its purpose is to maintain an air/fuelratio of 14.7 to 1 in order to reduceemissions. This test checks to see if thesolenoid dwell is varying.

Test Description:

This test is rather long and detailed. Referto vehicle service manual for the com-plete test procedure. Some important testprocedure highlights you need to payclose attention to are listed below.

1. Make sure engine is at operatingtemperature and running duringtest.

2. Refer to vehicle service manualfor multimeter hook-up instruc-tions.

3. Turn multimeter rotary switch to 6Cylinder Dwell position for all GMvehicles.

4. Run engine at 3000 RPM.

5. Make engine run both RICH andLEAN.

6. Watch multimeter display.

7. Multimeter display should varyfrom 10° to 50° as vehicle changesfrom lean to rich.

Typical Mixture ControlSolenoid Connection

Mixture ControlSolenoid

26

Measuring Fuel Injector Resistance

Fuel injectors are similar to solenoids.They contain a coil that is switched ONand OFF by the vehicle computer. Thistest measures the resistance of this coilto make sure it is not an open circuit.Shorted coils can also be detected if thespecific manufacturer resistance of thefuel injector is known.


Fig. 30Typical Fuel

Injector

Black Red



3. Turn multimeter rotary switch to200Ω range.

Touch RED and BLACK multimeterleads together and view reading ondisplay.

Display should read typically 0.2 -1.5Ω.

If display reading was greater than1.5Ω, check both ends of test leadsfor bad connections. If bad connec-tions are found, replace test leads.

4. Disconnect wiring harness fromfuel injector - Refer to vehicle ser-vice manual for procedure.

5. Connect RED and BLACK testleads across fuel injector pins.

Make sure you connect test leadsacross fuel injector and not the wir-ing harness.

6. Turn multimeter rotary switch todesired OHM range.

If the approximate resistance isunknown, start at the largestOHM range and decrease to theappropriate range as required.(see Setting the Range on page6)

7. View reading on display -Note range setting for cor-rect units.

• If display reading is 10Ω orless, subtract test lead resis-tance found in Step 3 fromabove reading.

• Compare reading to manu-facturers specifications forfuel injector coil resistance.

• This information is found invehicle service manual.

8. Test Results

Good Fuel Injector resistance: Re-sistance of fuel injector coil is withinmanufacturers specifications.

Bad Fuel Injector resistance: Resis-tance of fuel injector coil is not withinmanufacturers specifications.

NOTE: If resistance of fuel injectorcoil is within manufacturers specifi-cations, the fuel injector could stillbe defective. It is possible that thefuel injector is clogged or dirty andthat is causing your driveability prob-lem.

27

Testing Engine SensorsIn the early 1980’s, computer controls were installed in vehicles to meet FederalGovernment regulations for lower emissions and better fuel economy. To do its job, acomputer-controlled engine uses electronic sensors to find out what is happening inthe engine. The job of the sensor is to take something the computer needs to know,such as engine temperature, and convert it to an electrical signal which the computercan understand. The digital multimeter is a useful tool for checking sensor operation.

The Oxygen Sensor produces a voltageor resistance based on the amount ofoxygen in the exhaust stream. A lowvoltage (high resistance) indicates a leanexhaust (too much oxygen), while a highvoltage (low resistance) indicates a richexhaust (not enough oxygen). The com-puter uses this voltage to adjust the air/fuel ratio. The two types of O2 Sensorscommonly in use are Zirconia and Tita-nia. Refer to illustration for appearancedifferences of the two sensor types.


1. If engine is HOT, let it COOL downbefore proceeding.

2. Remove Oxygen Sensor from ve-hicle.



Titania-TypeOxygen Sensor

Zirconia-TypeOxygen Sensor

Exposedflat element

Flutes

Rich Lean

Red

5. Test heater circuit.

• If sensor contains 3 or more wires,then your vehicle uses a heated O2

sensor.

• Refer to vehicle service manual forlocation of heater pins.

• Connect RED test lead to eitherheater pin.

1-wire or 3-wire: Ground is sensor housing

2-wire or 4-wire: Ground is in sensor wiringharness

Ground

Black

Fig. 31

Oxygen (O2) Type Sensors

28

• Connect BLACK test lead to re-maining heater pin.

• Turn multimeter rotary switch to200Ω range.

• View reading on display.

• Compare reading to manufacturer'sspecification in vehicle servicemanual.

• Remove both test leads from sen-sor.

6. Connect BLACK test lead to sen-sor GROUND pin.

• If sensor is 1-wire or 3-wire, thenGROUND is sensor housing.

• If sensor is 2-wire or 4-wire, thenGROUND is in sensor wiring har-ness.

• Refer to vehicle service manual forOxygen Sensor wiring diagram.

7. Connect RED test lead to sensorSIGNAL pin.

8. Test Oxygen Sensor.

• Turn multimeter rotary switch to...

– 2V range for Zirconia Type Sen-sors.

– 200KΩ range for Titania TypeSensors.

• Light propane torch.

• Firmly grasp sensor with a pair oflocking pliers.

• Thoroughly heat sensor tip as hotas possible, but not “glowing.” Sen-sor tip must be at 660°F to operate.

• Completely surround sensor tipwith flame to deplete sensor ofoxygen (Rich Condition).

• Multimeter display should read...

– 0.6V or greater for Zirconia TypeSensors.

– an Ohmic(Resistance) value forTitania Type Sensors. Reading willvary with flame temperature.

• While still applying heat to sensor,move flame such that oxygen canreach sensor tip (Lean Condition).

• Multimeter display should read...

– 0.4V or less for Zirconia TypeSensors.

– an overrange condition for Tita-nia Type Sensors. (See Setting theRange on page 6.)

9. Repeat Step 8 a few times to verifyresults.

10. Extinguish Flame, let sensor cool,and remove test leads.

11. Test Results.

Good Sensor:

• Heater Circuit resistance is withinmanufacturer's specification.

• Oxygen Sensor output signalchanged when exposed to a richand lean condition.

Bad Sensor:

• Heater Circuit resistance is notwithin manufacturer's specification.

• Oxygen Sensor output signal didnot change when exposed to a richand lean condition.

• Oxygen sensor output voltagetakes longer than 3 seconds toswitch from a rich to a lean condi-tion.

29

1. If engine is HOT let it COOL downbefore proceeding.

Make sure all engine and transmis-sion fluids are at outside air tem-perature before proceeding with thistest!



4. Disconnect wiring harness fromsensor.

5. If testing Intake Air TemperatureSensor - Remove it from vehicle.

All other temperature sensors canremain on vehicle for testing.

6. Connect RED test lead to eithersensor pin.

7. Connect BLACK test lead to re-maining sensor pin.

8. Turn multimeter rotary switch todesired OHM range.If the approximate resistance is un-known, start at the largest OHMrange and decrease to the appropri-ate range as required. (See Settingthe Range on page 6)

RedBlack

Hair Dryer

TypicalIntake Air

TemperatureSensor

9. View and record reading on dis-play.

10. Disconnect multimeter test leadsfrom sensor and reconnect sen-sor wiring.This step does not apply to intake airtemperature sensors. For intake airtemperature sensors, leave multim-eter test leads still connected to sen-sor.

11. Heat up sensor.

If testing Intake Air Temperature Sen-sor:• To heat up sensor dip sensor tip

into boiling water, or...

• Heat tip with a lighter if sensor tip ismetal or a hair dryer if sensor tip isplastic.

• View and record smallest readingon display as sensor is heated.

• You may need to decrease therange to get a more accurate read-ing.

For all other temperature sensors:• Start engine and let idle until upper

radiator hose is warm.

• Turn ignition key OFF.

• Disconnect sensor wiring harnessand reconnect multimeter testleads.

• View and record reading on dis-play.

12. Test Results.

Good Sensor:

• Temperature sensors HOT resis-tance is at least 300Ω less than itsCOLD resistance.

• The key point is that the COLD re-sistance decreases with increasingtemperature.

Bad Sensor:

• There is no change between thetemperature sensors HOT resis-tance from the COLD resistance.

• The temperature sensor is an openor a short circuit.

A temperature sensor is a thermistor ora resistor whose resistance changes withtemperature. The hotter the sensor gets,the lower the resistance becomes. Typi-cal thermistor applications are enginecoolant sensors, intake air temperaturesensors, transmission fluid temperaturesensors, and oil temperature sensors.


Fig. 32

Temperature Type Sensors

30

Position Type SensorsPosition sensors are potentiometers ora type of variable resistor. They areused by the computer to determine po-sition and direction of movement of amechanical device. Typical position sen-sor applications are throttle positionsensors, EGR valve position sensors,and vane air flow sensors.


• If multimeter overranges on larg-est range, then sensor is an opencircuit and is defective.

7. Move RED test lead to sensor SIG-NAL pin.

• Refer to vehicle service manual forlocation of sensor SIGNAL pin.

8. Operate Sensor.

Fig. 33



3. Disconnect wiring harness fromsensor.

4. Connect Test Leads.

• Connect RED test lead to sensorPOWER pin.

• Connect BLACK test lead to sen-sor GROUND pin.

• Refer to vehicle service manual forlocation of sensor POWER andGROUND pins.


6. View and record reading on dis-play.

• Display should read some resis-tance value.

• If multimeter is overranging, adjustthe range accordingly. (See Set-ting the Range on page 6.)

Typical Toyota ThrottlePosition Sensor

Red Black

POWER GROUND

SIGNAL IDLE SWITCH

• To test these switches, follow theTesting Switches test procedureon page 13.

• When you are told to operateswitch, then move throttle linkage.

Vane Air Flow Sensor:

• Slowly open vane “door” fromclosed to open by pushing on itwith a pencil or similar object. Thiswill not harm sensor.

• Depending on hook-up, the dis-play reading will either increase ordecrease in resistance.

• The display reading should eitherstart at or end at the approximateresistance value measured in Step6.

• Some vane air flow sensors havean idle switch and an intake airtemperature sensor in addition to apotentiometer.

• To test idle switch see TestingSwitches on page 13.

• When you are told to operateswitch, then open vane “door”.

Throttle Position Sensor:

• Slowly move throttle linkagefrom closed to wide open posi-tion.

• Depending on hook-up, the dis-play reading will either increaseor decrease in resistance.

• The display reading should ei-ther start at or end at the ap-proximate resistance valuemeasured in Step 6.

• Some throttle position sensorshave an Idle or Wide OpenThrottle (WOT) switch in addi-tion to a potentiometer.

31

• To test intake air tempera-ture sensor see TemperatureType Sensors on page 29.

EGR Valve Position

• Remove vacuum hose fromEGR valve.

• Connect hand vacuum pumpto EGR valve.

• Gradually apply vacuum toslowly open valve. (Typi-cally, 5 to 10 in. of vacuumfully opens valve.)

• Depending on hook-up, thedisplay reading will eitherincrease or decrease in re-sistance.

• The display reading shouldeither start at or end at theapproximate resistancevalue measured in Step 6.

9. Test Results.

Good Sensor: D i s p l a yreading gradually increasesor decreases in resistance assensor is opened and closed.

Bad Sensor: There is nochange in resistance as sen-sor is opened or closed.

Manifold AbsolutePressure (MAP) andBarometric Pressure(BARO) SensorsThis sensor sends a signal to the com-puter indicating atmospheric pressureand/or engine vacuum. Depending onthe type of MAP sensor, the signal maybe a dc voltage or a frequency. GM,Chrysler, Honda and Toyota use a dcvoltage MAP sensor, while Ford uses afrequency type. For other manufactur-ers refer to vehicle service manual fortype of MAP sensor used.




3. Disconnect wiring harnc Û andvacuum line from MAP sensor.

4. Connect jumper wire between PinA on wiring harness and sensor.

5. Connect another jumper wire be-tween Pin C on wiring harnessand sensor.

6. Connect RED test lead to sensorPin B.

7. Connect BLACK test lead to goodvehicle ground.

8. Make sure test leads and jumperwires are not touching each other.

9. Connect a hand held vacuumpump to vacuum port on MAP sen-sor.

10. Turn Ignition Key ON, but do notstart engine!

11. Turn multimeter rotary switch to...

• 20V range for DC type MAP sen-sors.

• 4 Cylinder RPM position for Fre-quency type MAP sensors.

Fig. 34

Ground

Red

Black

TypicalGMMAP

Sensor

ToComputer

DCOnly

FrequencyOnly

32


DC Volts Type Sensor:

• Verify hand held vacuum pump isat 0 in. of vacuum.

• Display reading should be approxi-mately 3V or 5V depending onMAP sensor manufacturer.

Frequency Type Sensor:

• Verify hand held vacuum pump isat 0 in. of vacuum.

• Display reading should be approxi-mately 4770RPM ± 5% for FordMAP sensors only.

• For other frequency type MAP sen-sors refer to vehicle service manualfor MAP sensor specifications.

• It is O.K. if last two display digitschange slightly while vacuum isheld constant.

• Remember to multiply displayreading by 10 to get actual RPM.

• To convert RPM to Frequency orvice versa, use equation below.

Frequency = RPM30

(Equation Only Valid for Multimeterin 4 Cylinder RPM Position)

13. Operate Sensor.

• Slowly apply vacuum to MAP sen-sor - Never exceed 20 in. of vacuumbecause damage to MAP sensormay result.

• Display reading should decreasein voltage or RPM as vacuum toMAP sensor is increased.

• Refer to vehicle service manualfor charts relating voltage and fre-quency drop to increasing enginevacuum.

• Use equation above for Frequencyand RPM conversions.

14. Test Results.

Good Sensor:

• Sensor output vol tage orfrequency(RPM) are within manu-facturers specifications at 0 in. ofvacuum.

• Sensor output voltage or frequency(RPM) decrease with increasingvacuum.

Bad Sensor:

• Sensor output voltage or frequency(RPM) are not within manufactur-ers specifications at 0 in. ofvacuum.

• Sensor output voltage or frequency(RPM) do not change with increas-ing vacuum.

Mass Air Flow (MAF)SensorsThis sensor sends a signal to the com-puter indicating the amount of air enter-ing the engine. Depending on the sen-sor design, the signal may be a dc volt-age, low frequency, or high frequencytype. The CP7677 can only test the dcvoltage and low frequency type ofMAF sensors. The high frequency typesensors output a frequency that is toohigh for the CP7677 to measure. Thehigh frequency type MAF is a 3-pin sen-sor used on 1989 and newer GM ve-hicles. Refer to vehicle service manualfor the type of MAF sensor your vehicleuses.




3. Connect BLACK test lead to goodvehicle ground.

4. Connect RED test lead to MAFsignal wire.

• Refer to vehicle service manual forlocation of MAF signal wire.

• You may have to backprobe orpierce MAF signal wire in order tomake connection.

• Refer to vehicle service manual forbest way to connect to MAF signalwire.

5. Turn Ignition Key ON, but do notstart engine!

6. Turn multimeter rotary switch to...

33

8. Operate Sensor.

• Start engine and let idle.

• Display reading should...

- increase in voltage fromKey On Engine OFF for DCtype MAF sensors.

- increase in RPM from KeyOn Engine OFF for Low Fre-quency type MAF sensors.

• Rev Engine.

• Display reading should...

- increase in voltage from Idlefor DC type MAF sensors.

- increase in RPM from Idlefor Low Frequency type MAFsensors.

• Refer to vehicle servicemanual for charts relatingMAF sensor voltage or fre-quency (RPM) to increasingair flow.

• Use equation above for Fre-quency and RPM conver-sions.

Typical GM 1988 & olderLow Frequency type

MAF Sensor

Red

DCOnly

FrequencyOnly

Black

Ground

Fig. 35

• 20V range for DC type MAF sen-sors.

• 4 Cylinder RPM position for LowFrequency type MAF sensors.


DC Volts Type Sensor:

• Display reading should be approxi-mately 1V or less depending onMAF sensor manufacturer.

Low Frequency Type Sensor:

• Display reading should be approxi-mately 330RPM ± 5% for GM LowFrequency MAF sensors.

• For other Low Frequency type MAFsensors refer to vehicle servicemanual for MAF sensor specifications.

• It is O.K. if last two display digitschange slightly while Key is ON.

• Remember to multiply display read-ing by 10 to get actual RPM.

• To convert RPM to Frequency orvice versa, use equation below.

Frequency = RPM30

Equation Only Valid for Multim-eter in 4 Cylinder RPM Position

9. Test Results.

Good Sensor:

• Sensor output voltage or frequency(RPM) are within manufacturersspecifications at Key ON EngineOFF.

• Sensor output voltage or frequency(RPM) increase with increasing airflow.

Bad Sensor:

• Sensor output voltage or frequency(RPM) are not within manufactur-ers specifications at Key ON En-gine OFF.

• Sensor output voltage or frequency(RPM) do not change with increas-ing air flow.

34

Electrical Specifications

DC VoltsRange: 200mV, 2V, 20V, 200VAccuracy : ± (0.5% rdg + 5 dgts)

Range: 1000VAccuracy: ±(0.8% rdg + 5 dgts)

AC VoltsRange: 2V, 20V, 200VAccuracy : ± (0.8% rdg + 5 dgts)

Range: 750VAccuracy: ±(1.0% rdg + 4 dgts)

DC CurrentRange: 200mAAccuracy: ±(0.8% rdg + 5 dgts)

Range: 10AAccuracy: ±(1.2% rdg + 5 dgts)

ResistanceRange: 200Ω, 2KΩ, 20KΩ, 200KΩ, 2MΩAccuracy: ±(0.8% rdg + 5 dgts)

Range: 20MΩAccuracy: ±(1.5% rdg + 5 dgts)

DwellRange: 4CYL, 6CYL, 8CYLAccuracy: ±(3.0% rdg + 5 dgts)

RPMRange: 4CYL, 6CYL, 8CYLAccuracy: ±(3.0% rdg + 5 dgts)

Audible ContinuityBuzzer sounds at approximately lessthan 30-50 Ohms.

Auto TroubleShooter CP7677 OPERATING INSTRUCTIONS - Actron · PDF fileIgnition System Testing..... 19 - Ignition Coil Testing ..... 19 - Ignition System Wires ..... 21 - Hall Effect

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