P0742

Circuit Description
The Torque Converter Clutch (TCC) release switch is part of the Automatic Transmission Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.). The TFP Val. Position Sw. is mounted to the transmission valve body.
The TCC release switch is a normally-closed switch. The switch signals the Powertrain Control Module (PCM) that the TCC is released. Torque converter release fluid pressure acts on the switch contact, opening circuits 657/1804. When the voltage on the circuit is high, the PCM recognizes that the TCC is no longer engaged.
If the PCM detects that the TCC release switch is closed when the TCC is commanded OFF, then DTC P0742 sets. DTC P0742 is a type A DTC.

Conditions for Setting the DTC
^ No TP DTCs P0121, P0122 or P0123.
^ No Vehicle Speed Sensor (VSS) DTCs P0502 or P0503.
^ No TCC PWM Sol. Valve DTC P1860.
^ No TCC Release Switch DTC P1887.
^ The engine speed is greater than 500 RPM, and not in fuel shut off.
^ The TP is 14-45%.
^ The TCC is commanded OFF.
^ The transmission gear range indicates D4.
^ The time since the last gear range change is greater than 6 seconds.
^ The TCC release switch is closed for 6 occurrences.
^ All of the above conditions are met for 4 seconds.

Action Taken When the DTC Sets
^ The PCM illuminates the Malfunction Indicator Lamp (MIL).
^ The PCM commands the TCC ON at maximum capacity.
^ The PCM disables shift adapts.

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

Diagnostic Aids
^ Rapid fluctuation in line pressure could set DTC P0742.
^ Inspect for a pressure regulator condition.
^ Inspect for abnormal line pressure.
^ Inspect the wiring at the PCM, the transmission 20-way connector and all other circuit connecting points for the following conditions:
- A bent terminal
- A backed out terminal
- A damaged terminal
- Poor terminal tension
- A chafed wire
- A broken wire inside the insulation
- Moisture intrusion
- Corrosion
^ When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.
^ The customer may notice an engine stalling condition.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
4. This step looks for a switch status change when the engine is running. If TCC release fluid is present, the switch should be closed.
5. By disconnecting the transmission connector, the PCM should observe an open switch, indicating that the wiring is okay.
8. This step tests for a mechanical or hydraulic condition.