OBJECTIVES

Automatic Transmissions and Transaxles, Fourth EditionBy Tom Birch and Chuck Rockwood

© 2010 Pearson Higher Education, Inc.Pearson Prentice Hall - Upper Saddle River, NJ 07458

OBJECTIVES

After studying Chapter 13, the reader should be able to:1. Describe the problems that can occur in electrical

circuits.2. Test electrical circuits.3. Explain what a diagnostic trouble code (DTC) is

and how it can be used by the service technician.4. Retrieve DTCs.5. Perform the ASE tasks related to electronic

problem diagnosis and repair.



ELECTRONIC TRANSMISSION DIAGNOSIS

• Electronic shift controls require the transmission technician to learn additional diagnostic and test procedures.

• When diagnosing an electronic transmission, it must be determined if the cause is faulty electronic controls, a hydraulic system problem, or a mechanical system malfunction.



ELECTRONIC TRANSMISSION DIAGNOSIS

FIGURE 13-1 A diagnostic procedure for an electronically controlled transmission.



ELECTRICAL CIRCUIT PROBLEMS

• There are three common types of electrical problems: – Open Circuits– High-resistance Circuits– Low-resistance (short or ground).




FIGURE 13-2 An open circuit is a break in the circuit that will stop the current flow (a). Corroded or loose connections will cause high resistance that will reduce the current flow (b). (Courtesy of Chrysler Corporation)




FIGURE 13-3 A short circuit is a wire-to-wire connection that can reduce magnetic coil strength or allow current to flow to the wrong circuit (a) or a short to ground. (b is courtesy of Chrysler Corporation)




FIGURE 13-4 A ground or short-to-ground circuit occurs when damage to the insulation allows an electrical path to the metal of the vehicle (a). It can occur at a wire or inside a component (b). (Courtesy of Chrysler Corporation)



MEASURING ELECTRICAL COMPONENTS

• In the past, technicians used a test light, jumper wire, and analog volt-ohmmeter or multimeter (a combination ammeter, ohmmeter, and voltmeter) for troubleshooting automotive electrical problems.

• Today, the weathertight connectors make the use of a jumper wire very difficult




FIGURE 13-5 A fused jumper wire can be used to bypass portions of a circuit to determine where the problem is located (a). If the lights come on with the jumper wire installed, the problem is the fuse, switch, or wires to the battery (b).




FIGURE 13-6 A self-powered test light includes a battery and can be used to check for continuity (a). A nonpowered test light (b) can be used to determine if a point in a circuit has voltage (c).




FIGURE 13-6 (CONTINUED) A self-powered test light includes a battery and can be used to check for continuity (a). A nonpowered test light (b) can be used to determine if a point in a circuit has voltage (c).




FIGURE 13-7 Analog (a) and digital (b) multimeters. Do not use analog meters when testing electronic circuits unless instructed to do so. The bar graph and digital display are shown in (c ).




FIGURE 13-7 (CONTINUED) Analog (a) and digital (b) multimeters. Do not use analog meters when testing electronic circuits unless instructed to do so. The bar graph and digital display are shown in (c ).




FIGURE 13-8 Many electrical components, like this TPS, use weathertight connectors with latches to keep contacts clean and tight.




• Measuring Voltage– A voltmeter is used to

measure circuit voltage and voltage drop.

– Voltage is measured by connecting the negative (-) lead to ground and probing various points along the circuit with the positive (+) lead

FIGURE 13-9 The positive (+) voltmeter lead is connected to the positive (+) solenoid terminal, and the negative (-) lead is connected to ground. With ground-

controlled solenoids, the negative (-) lead is connected to the solenoid TCM terminal.




FIGURE 13-10 Voltage is measured by connecting one voltmeter lead (normally the negative) to ground, and probing the wire connections with the other lead. (Courtesy of Chrysler Corporation)




FIGURE 13-11 This meter is connected to measure the voltage drop across the resistor. (Courtesy of Fluke Corporation; reproduced with permission)



TECH TIP

• Ohm’s law includes a formula that shows the relationship of the three important electrical values.

FIGURE 13-12 This modernized version of Ohm’s law memory triangle shows the relationship between volts, current (amps), and resistance.




• Measuring Resistance• Measuring Amperage• Measuring Duty Cycle

FIGURE 13-13 A digital multimeter being used to measure resistance. Be sure to turn off or

disconnect the electrical power to the circuit when using ohmmeter functions. (Courtesy of Fluke

Corporation; reproduced with permission)




FIGURE 13-14 A digital multimeter is being used to measure current flow. (Courtesy of Fluke Corporation; reproduced with permission)




FIGURE 13-15 Inductive ammeters can be clipped over a wire to measure the current flow without disturbing the wire connections.




FIGURE 13-16 The jaws of the amp probe are around the wire, and the probe is connected to the DMM. The circuit is drawing 2.85 amps, which is read on the volts scale of the DMM.



TECH TIP

FIGURE 13-17 This graph shows the current flow to a solenoid. The dip near the center shows that the solenoid plunger has actually moved.



TECH TIP

FIGURE 13-18 A blown fuse has been modified by soldering a short wire to each test point (a). Replacing a circuit fuse with a modified fuse provides an easy location to check the circuit’s current flow (b). This handy ammeter, called a Fuse Buddy, can be easily inserted into the fuse box (c). Note the system fuse has been inserted into the tool to protect the circuit.




FIGURE 13-19 Measuring solenoid duty cycle is similar to a solenoid voltage check. Note that feed-controlled circuits should be read at + duty cycle while ground-controlled circuits use a – duty cycle.




• Scan Tools– Special tools to scan data

from the vehicle computers have been developed by most vehicle manufacturers.

FIGURE 13-20 Two generic scan tools designed to work with most vehicles. The Mastertech (a) uses

adapters to connect to the diagnostic connector and an application cartridge to provide data for a particular

vehicle. The Genisys scan tool (b) has software cartridges for many vehicles. Note that the screen of

(b) is showing the engine, transmission input, and transmission output rpm; transmission operating data

can also be shown (c). (a is courtesy of Vetronix; b and c are courtesy of OTC)




FIGURE 13-21 This DLC (diagnostic link connector) is under the instrument panel (a). Connecting a scan tool to the DLC allows it to display and operate vehicle functions (b).




FIGURE 13-22 The first letter of an OBD-II code identifies the function of the fault code area; transmission faults will begin with P. The first digit indicates if the DTC is generic or manufacturer specific. The second digit indicates the power train system; a 7 or 8 would indicate a transmission fault. The last two digits indicate the fault.




• Oscilloscopes• Interpreting

Measurements

FIGURE 13-23 The scope is displaying a secondary ignition pattern in which most spark plugs are firing at about 10 kV; one is at 25 kV (a). A digitalstyle speed

sensor pattern is shown in b; note the gap indicating a possible problem in the center of the pattern. (Courtesy

of Fluke Corporation; reproduced with permission)




FIGURE 13-24 This transmission wire diagram shows the wire colors and terminal numbers and how the wires are connected.



ELECTRICAL/ELECTRONIC SYSTEM REPAIR

• A faulty electrical component such as a switch, relay, blower motor, or clutch is usually repaired by removing and replacing (R&R) it with a new unit. – To splice a wire, you should:

FIGURE 13-25 The No. 2 VSS and park/neutral position switch on this transaxle can be replaced

rather easily.




FIGURE 13-26 A terminal is usually pushed into a connector until it locks into place (a). A pick tool is used to unlock the terminal for removal (b).




FIGURE 13-27 A wire stripping/crimping tool has an area designed to crimp wire terminals. A cutting area is used to cut insulation and pull it off the wire.




FIGURE 13-28 A splice can be made quickly by crimping a wire connector to the two wires.




FIGURE 13-29 A wire splice can be made by sliding the bared ends of the wires together, and then twisting them to hold them together. This connection should be soldered for security. (Courtesy of DaimlerChrysler Corporation)




FIGURE 13-30 A wire connection is soldered together using rosincore solder.



TECH TIP

FIGURE 13-31 (a) A repaired wire connection should be insulated by wrapping it tightly with tape or using shrink tubing (b). The tubing will shrink tightly in place when heated using a hot air gun.




FIGURE 13-32 A signal monitor has three LEDs and wire connections for the transmission harness. On a road test, the LEDs show the electrical signals, and these should occur in the proper order. (Courtesy of J. S.Popper Inc., www.jspopper.com)




• Recalibration– A speedometer that is reading incorrectly can be

recalibrated in some vehicles.– Recalibration is often necessary when a new TCM is

installed.– The process must be performed exactly as directed by

the manufacturer.– Adaptive Function Relearn

• Electronic Control System Cautions• Diagnostic Trouble Codes (DTCs)



TECH TIP

• If it becomes necessary to correct electronic speedometer readings when there is no recalibration process built into the vehicle’s operating system, an aftermarket device is available.

FIGURE 13-33 This recalibrator device can be connected into the wire connections to the VSS. The internal setting switches can be used to increase or decrease the rpm signal to correct the speedometer readings. (Courtesy of Autotrans)




FIGURE 13-34 Extreme care should be used when testing components displaying the electrostatic discharge (ESD) symbol. These components can be damaged by ESD.




FIGURE 13-35 These DTCs are vehicle-model specific. They indicate the nature of the faults for a 42LE transmission. (Courtesy of Chrysler Corporation)




FIGURE 13-36 This DRB II screen shows that no fault codes are stored in the TCM memory (a); it would display a screen similar to b if there were fault codes. (Courtesy of Chrysler Corporation)




FIGURE 13-37 A visual inspection of the transmission electrical connector ensures that the terminals are clean and in good shape as well as being completely engaged.




• Signal Monitor• Forcing Shifts Electrically• Clutch Volume Index• EMI Electronic Problems



ELECTRONIC COMPONENT AND CIRCUIT CHECKS• After the nature of the problem has been

determined, the faulty circuit or components should be checked to locate the exact cause.

• These are often fairly simple voltage, resistance, or current flow checks.

• These checks can often be made with the components mounted in their normal position.

• A breakout box or test box can be connected into the circuit to allow the technician to check voltage or resistance



ELECTRONIC COMPONENT AND CIRCUIT CHECKS

FIGURE 13-38 This 100-pin breakout box can be connected to a wiring harness to provide convenient points to make electrical checks. (Courtesy of SPX/O7C)




FIGURE 13-39 The external (a) and internal (b) wiring harnesses connect to the transmission electrical components.



ELECTRONIC COMPONENT AND CIRCUIT CHECKS• TCM Power Checks

– Battery– To make a battery load test, you should:

• TCC Checks• Solenoid Checks• Switch Checks• Speed Sensor Checks• Throttle Position Sensor Checks• Temperature Sensor Checks




FIGURE 13-40 TCM terminals 16 and 17 receive B + when the transmission relay is energized. This also sends B + to the solenoid and pressure switch assembly.




FIGURE 13-41 Ohmmeter A is connected to check for a grounded circuit: it should read infinite resistance. Ohmmeter B is measuring the resistance of the coil; if the leads are reversed, it will show a different resistance because of the diode.




FIGURE 13-42 Ohmmeter A is checking for a grounded solenoid coil; the reading should be infinite. Ohmmeter B is measuring the coil resistance; t should be within the specifications for this solenoid (a). Connecting a solenoid to a 12-V battery should cause it to operate (b). Make sure the battery is connected using the correct polarity in case the solenoid has an internal diode.




FIGURE 13-43 You should not be able to blow through this solenoid if it is not activated (a). If it is connected to a 12-V battery, it should make a “click,” and you should be able to blow through it.




FIGURE 13-44 A special tester being used to check a solenoid (a) and a pressure switch (b). The switch should either open or close when air is supplied. The solenoid should allow or block an air flow when activated.




FIGURE 13-45 The five switches inside this MLP switch complete a connection to ground in the various gear positions. (Courtesy of DaimlerChrysler Corporation)




FIGURE 13-46 A single-wire VSS can be checked by connecting one ohmmeter lead to the output terminal and the other lead to ground (a). Rotating the transmission output shaft should cause the ohmmeter to fluctuate from zero to infinite ohms. A two-wire VSS is checked as shown in (b). Ohmmeter A is measuring the speed sensor coil resistance; it should be within the specifications. Ohmmeter B is checking for a grounded coil; the reading should be infinite. (a is courtesy of Chrysler Corporation)




FIGURE 13-47 Switch and sensor operation can affect different phases of transmission operation.




FIGURE 13-48 An ohmmeter being used to check a throttle position sensor. After disconnecting the 5-V reference, a lead is connected to the two TPS terminals. As the throttle is opened, the needle should deflect between no resistance and high resistance.




FIGURE 13-49 A TPS can be checked by connecting a DC voltmeter to the output terminal and ground. The signal should increase as the throttle is opened and stay within specifications.




FIGURE 13-50 An ohmmeter connected to the two temperature sensor terminals should show that resistance will vary with the temperature. This sensor should have about 400 Ωat 70°C.



ELECTRONIC REPAIR JOB COMPLETION

• Road test the vehicle after any repair to verify proper operation.

• This test drive is similar to the diagnostic test drive. • You should also check to verify that all of the old

DTCs were cleared and no new DTCs were set. • Any problems found must be corrected before

returning the vehicle to the customer.



SUMMARY

1. An understanding of electrical circuits is essential for diagnosing and repairing electronic transmissions.

2. The tools used to diagnose transmission electrical failures include test lights, digital multimeters, scan tools, oscilloscopes, and specially designed testers.

3. When diagnosing an electrically controlled automatic transmission, one of the first steps is to determine if the trouble is mechanical, hydraulic, or electrical.



SUMMARY

4. Electrically controlled transmissions store a trouble code if a problem is identified by the PCM.

5. Testing the sensors and actuators involves basic electrical testing that can be done with a multimeter.



REVIEW QUESTIONS

1. The three major types of electrical problems are:a. _________b. _________c. _________

2. Electrical problems can show up as either _________ problems or be _________.

3. When a circuit is open, no _________ will flow.4. An increase in resistance will cause a _________ in current

flow.5. Excess resistance problems are located by measuring the

_________ _________ at the various parts of the circuit.6. When current bypasses the intended path, the problem is

known as a _________.



REVIEW QUESTIONS

7. A short where a bare wire touches ground is commonly called a _________ to _________.

8. The most practical meter for testing electrical components is a _________ _________.

9. Voltage drop is the amount of _________ used to move _________ through a load.

10. An _________ would be used to test a component that is out of the circuit.

11. A technician would use a _________ _________ to read the DTCs from an ECM.

12. An _________ would be an ideal tool to observe the operations of a circuit with changing electrical values.



REVIEW QUESTIONS13.When making solder connections, always use _________-core solder.14.The recommended three-step procedure for checking an electronically

controlled transmission is:a. _________b. _________c. _________

15.The most probable causes of electrical problems are _________ _________ and _________ _________ that move.

16.Four simple rules to follow when testing or working on electronically controlled transmissions are:a. Make sure that the ignition is _________ before disconnecting or connecting

the ECM.b. Make sure that the ignition is off before disconnecting or connecting any

_________ controlled components.c. Never touch the _________ or _________ components without first

grounding yourself.d. Use the proper_________ equipment.



REVIEW QUESTIONS

17.The ECM must have a good _________ source and a good _________ to operate properly.

18.The transmission solenoid must be tested both for _________ and _________ operation.

19.Throttle position sensors are checked for a _________ increase or decrease in meter reading as the throttle is opened and closed.

20.The temperature sensor can be checked by measuring the _________ at a known temperature.



CHAPTER QUIZ

1. Student A says that a short can occur if the internal wires in a component make contact. Student B says that a short causes a fuse to open, shutting off the current flow. Who is correct?a) Student Ab) Student Bc) Both A and Bd) Neither A nor B



CHAPTER QUIZ

1. Student A says that a short can occur if the internal wires in a component make contact. Student B says that a short causes a fuse to open, shutting off the current flow. Who is correct?a) Student Ab) Student Bc) Both A and Bd) Neither A nor B



CHAPTER QUIZ

2. Student A says that a check to determine if there is voltage at a component can be made using a voltmeter. Student B says that a test light is the best way to measure voltage at a component. Who is correct?a) Student Ab) Student Bc) Both A and Bd) Neither A nor B



CHAPTER QUIZ

2. Student A says that a check to determine if there is voltage at a component can be made using a voltmeter. Student B says that a test light is the best way to measure voltage at a component. Who is correct?a) Student Ab) Student Bc) Both A and Bd) Neither A nor B



CHAPTER QUIZ

3. When checking electronic transmission controls, you should not use an analog voltmeter or ordinary test light because theya) are obsolete.b) are slow and clumsy.c) draw too much current and can change or damage the

circuit.d) All of these



CHAPTER QUIZ

3. When checking electronic transmission controls, you should not use an analog voltmeter or ordinary test light because theya) are obsolete.b) are slow and clumsy.c) draw too much current and can change or damage the

circuit.d) All of these



CHAPTER QUIZ

4. Student A says that high resistance in a circuit can be located with a voltmeter. Student B says that excessive resistance can cause a circuit to work improperly. Who is correct?a) Student Ab) Student Bc) Both A and Bd) Neither A nor B



CHAPTER QUIZ

4. Student A says that high resistance in a circuit can be located with a voltmeter. Student B says that excessive resistance can cause a circuit to work improperly. Who is correct?a) Student Ab) Student Bc) Both A and Bd) Neither A nor B



CHAPTER QUIZ

5. When checking electronic transmission controls, you should use a digital meter that has at leasta) 100 ohms of resistance.b) 10 M ohms of internal resistance.c) 10 M ohms of external resistance.d) Any of the above



CHAPTER QUIZ

5. When checking electronic transmission controls, you should use a digital meter that has at leasta) 100 ohms of resistance.b) 10 M ohms of internal resistance.c) 10 M ohms of external resistance.d) Any of the above



CHAPTER QUIZ

6. Student A says that the only difference between an analog meter and a digital meter is the readout. Student B says that an analog meter could damage an electronic circuit. Who is correct?a) Student Ab) Student Bc) Both A and Bd) Neither A nor B



CHAPTER QUIZ

6. Student A says that the only difference between an analog meter and a digital meter is the readout. Student B says that an analog meter could damage an electronic circuit. Who is correct?a) Student Ab) Student Bc) Both A and Bd) Neither A nor B



CHAPTER QUIZ

7. Student A says that it is not a good practice to pierce wire insulation during testing. Student B says that if a wire is pierced during testing, it should be sealed to prevent corrosion problems. Who is correct?a) Student Ab) Student Bc) Both A and Bd) Neither A nor B



CHAPTER QUIZ

7. Student A says that it is not a good practice to pierce wire insulation during testing. Student B says that if a wire is pierced during testing, it should be sealed to prevent corrosion problems. Who is correct?a) Student Ab) Student Bc) Both A and Bd) Neither A nor B



CHAPTER QUIZ

8. Student A says that a voltmeter is used to check for unwanted resistance in an operational circuit. Student B says that an ohmmeter is used to check resistance in an operational circuit. Who is correct?a) Student Ab) Student Bc) Both A and Bd) Neither A nor B



CHAPTER QUIZ

8. Student A says that a voltmeter is used to check for unwanted resistance in an operational circuit. Student B says that an ohmmeter is used to check resistance in an operational circuit. Who is correct?a) Student Ab) Student Bc) Both A and Bd) Neither A nor B



CHAPTER QUIZ

9. Student A says that a scan tool can be used in place of a voltmeter. Student B says that a scan tool is used to communicate with the vehicle’s ECM. Who is correct?a) Student Ab) Student Bc) Both A and Bd) Neither A nor B



CHAPTER QUIZ

9. Student A says that a scan tool can be used in place of a voltmeter. Student B says that a scan tool is used to communicate with the vehicle’s ECM. Who is correct?a) Student Ab) Student Bc) Both A and Bd) Neither A nor B



CHAPTER QUIZ

10.Student A says that during a road test if the electronic controls are disabled and the problem does not change, the problem is not the electronic controls. Student B says that the solenoids can be operated by a special tool to check their operation during a road test. Who is correct?a) Student Ab) Student Bc) Both A and Bd) Neither A nor B



CHAPTER QUIZ

10.Student A says that during a road test if the electronic controls are disabled and the problem does not change, the problem is not the electronic controls. Student B says that the solenoids can be operated by a special tool to check their operation during a road test. Who is correct?a) Student Ab) Student Bc) Both A and Bd) Neither A nor B



CHAPTER QUIZ

11.Student A says that all electrical problems will set a code. Student B says that when the trouble codes are cleared, the problem is repaired. Who is correct?a) Student Ab) Student Bc) Both A and Bd) Neither A nor B



CHAPTER QUIZ

11.Student A says that all electrical problems will set a code. Student B says that when the trouble codes are cleared, the problem is repaired. Who is correct?a) Student Ab) Student Bc) Both A and Bd) Neither A nor B



CHAPTER QUIZ

12.A common problem with electronically controlled transmissions is a bada) electronic control unit.b) throttle position sensor.c) vehicle speed sensor.d) electrical connection.



CHAPTER QUIZ

12.A common problem with electronically controlled transmissions is a bada) electronic control unit.b) throttle position sensor.c) vehicle speed sensor.d) electrical connection.



CHAPTER QUIZ

13.Student A says that you can ruin an electronic control unit by touching its terminals with your finger. Student B says that you can ruin a solenoid by connecting it to a battery backward. Who is correct?a) Student Ab) Student Bc) Both A and Bd) Neither A nor B



CHAPTER QUIZ

13.Student A says that you can ruin an electronic control unit by touching its terminals with your finger. Student B says that you can ruin a solenoid by connecting it to a battery backward. Who is correct?a) Student Ab) Student Bc) Both A and Bd) Neither A nor B



CHAPTER QUIZ

14.When testing a pressure switch, it should showa) an open circuit without pressure at the switch.b) a complete circuit with pressure at the switch.c) a complete circuit without pressure at the switch.d) All of the above, depending on the switch



CHAPTER QUIZ

14.When testing a pressure switch, it should showa) an open circuit without pressure at the switch.b) a complete circuit with pressure at the switch.c) a complete circuit without pressure at the switch.d) All of the above, depending on the switch



CHAPTER QUIZ

15.Student A says that the voltage to the ECM is not as important as the voltage to the output solenoid. Student B says that the ECM must have a good ground connection. Who is correct?a) Student Ab) Student Bc) Both A and Bd) Neither A nor B



CHAPTER QUIZ

15.Student A says that the voltage to the ECM is not as important as the voltage to the output solenoid. Student B says that the ECM must have a good ground connection. Who is correct?a) Student Ab) Student Bc) Both A and Bd) Neither A nor B



CHAPTER QUIZ

16.Student A says that torque converter clutch operation can be easily checked on a road test by lightly stepping on the brake pedal and watching the tachometer for a change in speed. Student B says that the torque converter clutch can be tested using a scan tool to operate the circuit. Who is correct?a) Student Ab) Student Bc) Both A and Bd) Neither A nor B



CHAPTER QUIZ

16.Student A says that torque converter clutch operation can be easily checked on a road test by lightly stepping on the brake pedal and watching the tachometer for a change in speed. Student B says that the torque converter clutch can be tested using a scan tool to operate the circuit. Who is correct?a) Student Ab) Student Bc) Both A and Bd) Neither A nor B



CHAPTER QUIZ

17.Student A says that a solenoid can be tested by checking the current flow. Student B says that a solenoid can be tested using an ohmmeter. Who is correct?a) Student Ab) Student Bc) Both A and Bd) Neither A nor B



CHAPTER QUIZ

17.Student A says that a solenoid can be tested by checking the current flow. Student B says that a solenoid can be tested using an ohmmeter. Who is correct?a) Student Ab) Student Bc) Both A and Bd) Neither A nor B



CHAPTER QUIZ

18.When testing a solenoid with an ohmmeter, reversing the test leads will check thea) transistor.b) triode.c) diode.d) winding.



CHAPTER QUIZ

18.When testing a solenoid with an ohmmeter, reversing the test leads will check thea) transistor.b) triode.c) diode.d) winding.



CHAPTER QUIZ

19.Student A says that all transmission pressure switches are the same. Student B says that transmission pressure switches can be either normally open or normally closed. Who is correct?a) Student Ab) Student Bc) Both A and Bd) Neither A nor B



CHAPTER QUIZ

19.Student A says that all transmission pressure switches are the same. Student B says that transmission pressure switches can be either normally open or normally closed. Who is correct?a) Student Ab) Student Bc) Both A and Bd) Neither A nor B



CHAPTER QUIZ

20.When electrical or electronic repairs are completed the vehicle should bea) taken for a complete test drive.b) returned to the customer.c) held for several days to confirm the repair.d) All of the above



CHAPTER QUIZ

20.When electrical or electronic repairs are completed the vehicle should bea) taken for a complete test drive.b) returned to the customer.c) held for several days to confirm the repair.d) All of the above

OBJECTIVES

Documents

pearson higher education

editionby tom birch

chuck rockwood

test electrical circuits

automotive electrical

transmission technician

electronic problem diagnosis

faulty electronic controls