P0742

Circuit Description
The torque converter clutch (TCC) release switch is part of the automatic transmission fluid pressure manual valve position switch (TFP Valve Position Switch). The TFP Valve Position Switch 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 Throttle Position (TP) sensor DTCs P0121, P0122 or P0123.
^ No Vehicle Speed Sensor (VSS) DTCs P0502 or P0503.
^ No TCC PWM Solenoid 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 angle 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.
^ All of the above conditions are met at least 6 times for 4 seconds each.

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 freezes shift adapts.
^ The PCM stores DTC P0742 in PCM history.

Conditions for Clearing the MIL/DTC
^ A scan tool clears the DTC from the PCM history.
^ The PCM clears the DTC from the PCM history if the vehicle completes 40 consecutive warm-up cycles without an emission related diagnostic fault occurring.
^ The PCM cancels the DTC default actions when the fault no longer exists and the ignition switch 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.
3. If release pressure is shown with the engine OFF, there could be an open in the circuit. This could cause DTC P1887 to set.
4. With the engine running, release pressure should be present. The TCC release switch should be open.
5. By disconnecting the transmission connector, the PCM should observe an open switch, indicating that the wiring is OK.
10. This step tests for a mechanical or hydraulic condition.