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COMPUTERS AND INPUT COMPUTERS AND INPUT SENSORSSENSORS

CHAPTER 8CHAPTER 8

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VOLTAGE SIGNALSVOLTAGE SIGNALS

ANALOG VOLTAGE SIGNALSANALOG VOLTAGE SIGNALS– VARIABLE VOLTAGE SIGNALVARIABLE VOLTAGE SIGNAL– COMPUTERS INPUTS ARE USUALLY COMPUTERS INPUTS ARE USUALLY

ANALOG TYPE SIGNALSANALOG TYPE SIGNALS– EASY TO DIAGNOSE WITH DVOMEASY TO DIAGNOSE WITH DVOM– DIRECT CURRENT OR ALTERNATING DIRECT CURRENT OR ALTERNATING

CURRENTCURRENT

Pg 153CPg 153C

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DIGITAL VOLTAGE DIGITAL VOLTAGE SIGNALSSIGNALS

VOLTAGE IS EITHER HIGH OR LOW VOLTAGE IS EITHER HIGH OR LOW IN A GIVEN TIME PERIODIN A GIVEN TIME PERIOD

COMPUTER USES AND PROCESSES COMPUTER USES AND PROCESSES INFORMATION IN DIGITAL INFORMATION IN DIGITAL LANGUAGE (BINARY 0 or 1)LANGUAGE (BINARY 0 or 1)

SOME INPUTS PRODUCE A SQUARE SOME INPUTS PRODUCE A SQUARE WAVE SIGNAL WAVE SIGNAL

Pg 154CPg 154C

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COMPUTER OPERATIONCOMPUTER OPERATION

INPUT CONDITIONINGINPUT CONDITIONING– AMPLIFICATIONAMPLIFICATION– ANALOG TO DIGITAL CONVERSIONANALOG TO DIGITAL CONVERSION– SOME A/D CONVERTER EXTERNAL TO SOME A/D CONVERTER EXTERNAL TO

MAIN PROCESSOR. (LIKE FORD MAIN PROCESSOR. (LIKE FORD PROGRAMMABLE SPEED ONLY PROGRAMMABLE SPEED ONLY MEMORY - PSOM)MEMORY - PSOM)

Pg 155CPg 155C

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COMPUTER MEMORYCOMPUTER MEMORY

RAM - RANDOM ACCESS MEMORYRAM - RANDOM ACCESS MEMORY– TEMPORARY STORAGETEMPORARY STORAGE– VOLATILE OR NON-VOLATILEVOLATILE OR NON-VOLATILE

ROM - READ ONLY MEMORYROM - READ ONLY MEMORY PROM - PROGRAMMABLE READ PROM - PROGRAMMABLE READ

ONLY MEMORYONLY MEMORY– TELLS MICROPROCESSOR HOW TELLS MICROPROCESSOR HOW

VEHICLE IS EQUIPPEDVEHICLE IS EQUIPPED

Pg 159CPg 159C

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COMPUTER COMPUTER PROGRAMMED STRATEGYPROGRAMMED STRATEGY OPEN LOOP - CLOSED LOOPOPEN LOOP - CLOSED LOOP ADAPTIVE STRATEGYADAPTIVE STRATEGY

– ABILITY OF COMPUTER TO LEARN ABILITY OF COMPUTER TO LEARN FROM PAST EXPERIENCE.FROM PAST EXPERIENCE.

– COMPENSATES FOR WEARCOMPENSATES FOR WEAR Will lose learned strategy if: Will lose learned strategy if:

– BATTERY DISCONNECTEDBATTERY DISCONNECTED

– WHEN MAJOR COMPONENT REPLACEDWHEN MAJOR COMPONENT REPLACED

– NEW VEHICLENEW VEHICLE

Pg 160CPg 160C

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INPUT PROCESSINGINPUT PROCESSING

ROM LOOK UP TABLES (Pg 162C)ROM LOOK UP TABLES (Pg 162C) COMPUTER TAKES ALL INPUT COMPUTER TAKES ALL INPUT

INFO BEFORE MAKING DECISIONINFO BEFORE MAKING DECISION ONE WIRE INPUT (Pg 140L & 154L)ONE WIRE INPUT (Pg 140L & 154L) TWO WIRE INPUT (Pg 142L & 143L)TWO WIRE INPUT (Pg 142L & 143L) THREE WIRE INPUT (Pg 144L)THREE WIRE INPUT (Pg 144L) FOUR WIRE INPUT (Pg 146L)FOUR WIRE INPUT (Pg 146L)

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PINPOINT TESTINGPINPOINT TESTING

MOST REPAIR MANUALS TELL TO MOST REPAIR MANUALS TELL TO CAUSE OPPOSITE CODECAUSE OPPOSITE CODE

OHMMETER VS. VOLTMETEROHMMETER VS. VOLTMETER FREQUENCY INPUT TESTINGFREQUENCY INPUT TESTING LAB SCOPE USELAB SCOPE USE BLOCK LEARN - INTEGRATORBLOCK LEARN - INTEGRATOR

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OXYGEN SENSORSOXYGEN SENSORS

1,2,3,4 Wire s1,2,3,4 Wire s EGO, HEGOEGO, HEGO Lean Low VoltsLean Low Volts Rich High VoltsRich High Volts Zirconia TypeZirconia Type Titania TypeTitania Type DVOM or Lab Scope DVOM or Lab Scope

Only!!!Only!!! PAGE 168CPAGE 168C

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ECT/ACT SENSORSECT/ACT SENSORS

THERMISTORS HIGH RESISTANCE THERMISTORS HIGH RESISTANCE COLD AND LOWER RESISTANCE HOTCOLD AND LOWER RESISTANCE HOT

PG 142LPG 142L

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THROTTLE POSITION THROTTLE POSITION SENSORS (TPS)SENSORS (TPS)

ROTARY AND LINEARROTARY AND LINEAR MUST BE SMOOTH VOLTAGE CHANGEMUST BE SMOOTH VOLTAGE CHANGE BEST TO USE A LAB SCOPE FOR TESTBEST TO USE A LAB SCOPE FOR TEST

PG 145LPG 145L

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THROTTLE SWITCHTHROTTLE SWITCH

Four Wire SensorFour Wire Sensor Used on alot of Foreign Cars and TrucksUsed on alot of Foreign Cars and Trucks Adjustment is criticalAdjustment is critical Some switches used as Fuel Pump Shut Off Some switches used as Fuel Pump Shut Off

Pg 146LPg 146L

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MANIFOLD ABSOLUTE MANIFOLD ABSOLUTE PRESSURE SENSORPRESSURE SENSOR

Senses differences between atmospheric Senses differences between atmospheric pressure and manifold vacuum.pressure and manifold vacuum.

Must use specialized equipment to testMust use specialized equipment to test Sometimes used for BARO Input informationSometimes used for BARO Input information

Pg 147LPg 147L

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MASS AIR FLOW SENSORSMASS AIR FLOW SENSORS

VANE TYPEVANE TYPE Commonly used on Commonly used on

foreign Carsforeign Cars Test with DVOM or Test with DVOM or

Lab ScopeLab Scope Plate movement Plate movement

proportional to Air proportional to Air FlowFlow

Other InputsOther Inputs

HOT WIRE TYPE HOT WIRE TYPE or GRID TYPEor GRID TYPE

Use Frequency Test Use Frequency Test Map Frequency Map Frequency

should always be a should always be a straight line straight line transition with rpm.transition with rpm.

Tap TestTap Test

Pg 151LPg 151L Pg 152LPg 152L

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KNOCK SENSORSKNOCK SENSORS

PIEZOELECTRIC CRYSTALPIEZOELECTRIC CRYSTAL Produces a frequency and changes it to a Produces a frequency and changes it to a

voltage before sending to PCMvoltage before sending to PCM TAP TEST, DVOM, FREQ or OHMMETER TAP TEST, DVOM, FREQ or OHMMETER

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EGR SENSORSEGR SENSORS EVP Linear SensorEVP Linear Sensor Must test mechanical and electricalMust test mechanical and electrical Many different types of EGR & ``EGR Many different types of EGR & ``EGR

Controls and EGR SensorsControls and EGR Sensors Most EVP’s send a Analog signalMost EVP’s send a Analog signal Lots of Driveability ProblemsLots of Driveability Problems EGR problems can be caused by other EGR problems can be caused by other

InputsInputs

Pg 154LPg 154LPg 317LPg 317L

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VEHICLE SPEED SENSORSVEHICLE SPEED SENSORS

AC SIGNAL (ANALOG)AC SIGNAL (ANALOG) LOCATED DIFFERENT PLACESLOCATED DIFFERENT PLACES SPEED BUFFER OR PSOMSPEED BUFFER OR PSOM CAN CAUSE TCC, CRUISE, SPEEDOMETER CAN CAUSE TCC, CRUISE, SPEEDOMETER

PROBLEMSPROBLEMS

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NEUTRAL DRIVE SWITCHNEUTRAL DRIVE SWITCH

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OUTPUTSOUTPUTS

ACTUATORSACTUATORS– SOLENOIDSSOLENOIDS– RELAYSRELAYS– DISPLAYS DISPLAYS

CONTROLLED BY DRIVERSCONTROLLED BY DRIVERS TRANSISTORS OR GROUPS OF TRANSISTORS OR GROUPS OF

TRANSISTORSTRANSISTORS

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STUDY HARD AND STUDY HARD AND ABSORB!!ABSORB!!