P0742 Torque converter clutch stuck on

P0742 code - Theory of operation the transmission control module (TCM) constanly monitor the amount of torque converter slippage. When the torque converter cluth (TCC) is open slippage is expected to be above a threshold. If the slippage is less expected when the TCC assumes that the TCC is stuck on. 

When monitored this DTC the ignition on, TCM not in initialization phase, nop 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 impalusible DTCs, Engine speed greater than 450 rpm, no shift in progress, 1,2,3,4 or 5 enganed and the TCM torque converter status is OPEN. Set condition this DTC the 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 DTC P0742 code :

- TCC solenoid control circuit shorted to ground

- TCC solenoid control circuit shorted to another circuit

- Internal transmission

- Lockup control valve sticking in its bore

- Leaking tcc solenoid

- Torque converter

- Transmission control module (TCM)

Diagnostic test P0742 code

Step 1. Check if engine stalls or stumbles in gear 

Turn the ignition off to the lock position. Disconnect the electrohydraulic control unit assembly harness connector. Check connector clean/repair as necessary.

Start the engine. With the brakes firmly applied, shift the gear selector into drive.

Did the engine stall stumble?

Yes, repair internal transmission in accordance with the service information. Pay particular attention to the components related to the TCC such as lockup control valve sticking in its bore or a leaking TCC solenoid.

No, go to step 2

Step 2. TCC solenoid control circuit short to ground

Turn the ignition off to the lock position. Disconnect the TCM C2 harness connector. Check connectors clean/repair as necessary.

Measure the resistance between ground and the TCC solenoid control circuit.

Is the resistance below 5.0 Ohms?

Yes, repair the TCC solenoid control circuit for a short to ground.

No, go to step 3.

Step 3. TCC solenoid control circuit short to another circuit

Measure the resistance between the TCC solenoid control circuit and all other circuits in the transmission electronic control unit assembly harness connector.

Is the resistance below 5.0 Ohms between 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 aguide, check the transmission control module (TCM) terminals for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace the TCM in accordance with the service information. Perform NAG1 Transmission Verification Test.

Share this post