With 4L80 Transmission

Diagnostic Chart:

Wiring Diagram:

Circuit Description
When the Vehicle Control Module (VCM) detects low torque converter slip when the Torque Converter Clutch (TCC) is commanded OFF, then Diagnostic Trouble Code (DTC) P0742 sets. DTC P0742 is a type D DTC. For California emission vehicles DTC P0742 is a type B DTC.

Conditions for Setting the DTC
The following conditions occur once per TCC cycle two consecutive times:

^ No Throttle Position (TP) Sensor DTCs P0121 or P0122.
^ No Output Shaft Speed (OSS) DTC P0502.
^ No Automatic Transmission Input Shaft Speed (A/T ISS) Sensor DTCs P0716 or P0717.
^ No TCC DTCs P0741 or P1860.
^ No TFP Valve Position Sw. DTC P1810.
^ No MAP Sensor DTCs P0106, P0107, or P0108.
^ The engine must run more than 475 RPM for greater than 7 seconds and not in fuel cutoff.
^ The engine torque must be 75 Nm (60 lb. ft) to:

- 333 Nm (265 lb. ft).

^ The TFP Val. Position Sw. must indicate D4.
^ The commanded gear must be 2nd, 3rd, or 4th.
^ The Throttle Position must be greater than 10%.
^ The TCC slip speed must be -15 to +20 RPM for at least 3.25 seconds.
^ All conditions met for 3 occurrences.

Action Taken When the DTC Sets

^ The VCM commands D2 maximum line pressure.
^ The VCM freezes shift adapts.
^ The VCM illuminates the Malfunction Indicator Lamp (MIL) for California emissions vehicles.

Conditions for Clearing the DTC

1. The VCM turns OFF the MIL after three consecutive ignition cycles without a failure reported.
2. A scan tool can clear the DTC from the VCM history. The VCM clears the DTC from the VCM history if the vehicle completes 40 warm-up cycles without a failure reported.
3. The VCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the VCM.

Diagnostic Aids

^ if the TCC is mechanically stuck On with the parking brake applied and any gear range selected, the TCC fluid mechanically applies the TCC. TCC fluid mechanically applying the TCC can cause an engine stall.
^ A stuck TP Sensor sets DTC P0742.
^ First diagnose and clear any engine DTCs or TP Sensor codes that are present. Then inspect for any transmission DTCs that may have reset.

Test Description
The numbers below refer to the step numbers on the diagnostic table.

3. This step tests the mechanical state of the ICC. When the VCM commands the ICC solenoid OFF, the slip speed should increase.