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 circuit 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) DTCs P0121, P0122, or P0123

^ No Vehicle Speed (VSS) sensor DTCs P0502 or P0503

^ No TCC Pulse Width Modulated (PWM) Sol. Valve DTC P1860

^ No TCC Release DTC P1887

^ The engine is running.

^ The TP is 14-45%.

^ The TCC is commanded OFF.

^ Not in fuel shut off.

^ The gear range change is greater than 3 seconds.

^ The TCC release switch is closed, on 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 disables shift adapts.

^ The PCM commands the TCC ON at maximum capacity.


Conditions for Clearing the MIL/DTC

^ The PCM turns OFF the MIL after three consecutive ignition cycles 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 problem.

^ Inspect for abnormal line pressure.

^ Inspect the wiring for poor electrical connections at the PCM. Inspect the wiring for poor electrical connections at the transmission 20-way connector. Look for the following problems:

- A bent terminal

- A backed out terminal

- A damaged terminal

- Poor terminal tension

- A chafed wire

- A broken wire inside the insulation

^ 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 problem.


Test Description

The numbers below refer to the step numbers on the diagnostic chart.

4. This step looks for a switch status change when the engine is running. If TCC release oil 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 problem.