P0742

P0742-TORQUE CONVERTER CLUTCH STUCK ON





For a complete wiring diagram Refer to Diagrams/Electrical Electrical Diagrams


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 Nm (74.0 ft.lbs.) for period of 1.0 second.







Always perform the NAG1 Pre-Diagnostic Troubleshooting procedure before proceeding. NAG1 - Pre-Diagnostic Troubleshooting Procedure


Diagnostic Test


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.


NOTE: Check connectors - Clean/repair as necessary.

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.
- Perform NAG1 TRANSMISSION VERIFICATION TEST. NAG1 Transmission Verification Test

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.


NOTE: Check connectors - Clean/repair as necessary.

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. NAG1 Transmission Verification Test

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).
- Perform NAG1 TRANSMISSION VERIFICATION TEST. NAG1 Transmission Verification Test

No

- Using the schematics as a guide, 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.
- Perform NAG1 TRANSMISSION VERIFICATION TEST. NAG1 Transmission Verification Test