P0742-TORQUE CONVERTER CLUTCH STUCK ON
For a complete wiring diagram Refer to Section 8W
Theory of Operation
The Transmission Control Module (TCM) constantly monitors the amount of torque converter slippage. When the torque converter clutch (TCC) is open the slippage is expected to be above a threshold. If the slippage is less then expected when the TCC is open, the TCM assumes that the TCC is stuck on.
- When Monitored:
Ignition on, TCM not in initialization phase, No input speed sensor 1 or 2 (N2–N3) DTCs, No CAN bus or ECM DTCs, No CAN engine speed signal or engine torque signal not implausible DTCs, Engine speed greater than 450 rpm, No shift in progress, Gear 1, 2, 3, 4 or 5 engaged, and the TCM torque converter status is OPEN
- Set Condition:
Engine RPM (Turbine Speed) is greater than 30 RPM when engine torque less than 100 N·m (74.0 ft.lbs.) for period of 1.0 second.
| Possible Causes |
| (T75) TCC SOLENOID CONTROL CIRCUIT SHORT TO GROUND |
| (T75) TCC SOLENOID CONTROL CIRCUIT SHORT TO ANOTHER CIRCUIT |
| INTERNAL TRANSMISSION |
| LOCKUP CONTROL VALVE STICKING IN ITS BORE |
| LEAKING TCC SOLENOID |
| TORQUE CONVERTER |
| TRANSMISSION CONTROL MODULE |
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)
Diagnostic Test
1. CHECK IF ENGINE STALLS OR STUMBLES IN GEARTurn the ignition off to the lock position.
Disconnect the Electrohydraulic Control Unit Assembly harness connector.
Start the engine.
With the brakes firmly applied, shift the gear selector into Drive.
Did the engine stall or stumble?
Yes
- Repair internal transmission. Pay particular attention to the components related to the TCC such as the Lockup Control Valve sticking in its bore or a leaking TCC Solenoid. Refer to the Service Information for the proper repair procedures.
- Perform NAG1 TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)
No
- Go To 2
2. (T75) TCC SOLENOID CONTROL CIRCUIT SHORT TO GROUND
Turn the ignition off to the lock position.
Disconnect the TCM C2 harness connector.
Measure the resistance between ground and the (T75) TCC Solenoid Control circuit.
Is the resistance below 5.0 ohms?
Yes
- Repair the (T75) TCC Solenoid Control circuit for a short to ground.
- Perform NAG1 TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)
No
- Go To 3
3. (T75) TCC SOLENOID CONTROL CIRCUIT SHORT TO ANOTHER CIRCUIT
Measure the resistance between the (T75) TCC Solenoid Control circuit and all other circuits in the Transmission Electrohydraulic Control Unit Assembly harness connector.
Is the resistance below 5.0 ohms between the (T75) TCC Solenoid Control circuit and all other circuits in the Transmission Electrohydraulic Control Unit Assembly harness connector?
Yes
- Repair the (T75) TCC Solenoid Control circuit for a short to another circuit(s).
No
- Using the schematics as a guide, check the Transmission Control Module (TCM) pins, terminals, and connectors for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace the TCM per the Service Information. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES/TRANSMISSION CONTROL MODULE - REMOVAL)
- Perform NAG1 TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)