With 4 Speed Automatic

P0742 WITH 4 SPEED AUTOMATIC

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION

The Torque Converter Clutch Solenoid Valve (TCC Sol. Valve) is a pulse width modulated solenoid. The Powertrain Control Module (PCM) energizes the TCC Sol. Valve by grounding circuit 418. When vehicle operating conditions are appropriate for TCC application, the PCM begins the TCC duty cycle at approximately 68%. The PCM then increases the duty cycle up to 93%, in order to achieve full TCC-apply pressure.

When the TCC Sol. Valve is de-energized, the solenoid blocks filtered 2-3 drive fluid, and allows TCC signal fluid to exhaust. When energized, the solenoid modulates fluid into the TCC signal fluid circuit. When fully energized, modulation stops, and the solenoid blocks both 2-3 drive fluid and TCC signal fluid exhaust.

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.

When 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 TCC Release DTC P1887

^ The engine is running.

^ The Throttle Position (TP) is greater than 20%.

^ The TCC is commanded OFF.

^ The TCC release switch is closed, on two occurrences.

^ All of the above conditions are met for 8 seconds.

ACTION TAKEN WHEN THE DTC SETS

^ The PCM illuminates the Malfunction Indicator Lamp (MIL).

^ DTC P0742 is stored in the PCM history.

^ The PCM freezes shift adapts from being updated.

^ The PCM commands the TCC ON.

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 high or low 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 conditions:

- 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 condition, 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. This Step tests for a TCC release switch status change when the engine is running. If TCC release oil is present, the switch should be open.

4. If you disconnect the transmission connector, the PCM should recognize an open TCC Release switch. This indicates the wiring from the transmission connector to the PCM is OK.

12. This Step tests circuit 418 from the transmission connector to the TFP Val. Position Sw. for a short to ground.

17. This Step ensures that the TCC release switch is in good working condition.

19. This Step tests the TCC circuit for a mechanical or hydraulic problem.