P0742

4T40-E AUTOMATIC TRANSAXLE 5A- 115 DIAGNOSTIC TROUBLE CODE (DTC) P0742 TORQUE CONVERTER CLUTCH CIRCUIT STUCK ON





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 502. 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 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.
Torque Converter release fluid pressure acts on the switch contact, opening the circuit, signaling the PCM that the TCC is released. 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.

Conditions For Setting The DTC
- No TCC release DTC P1887.
- No TP DTC P1791.
- Engine running.
- Time since last manual gear select lever change is greater than three seconds.
- TP is greater than 20%.
- TCC commanded off.
- TCC release switch is closed.
- All the above conditions met for eight seconds.

Action Taken When The DTC Sets
- The PCM will illuminate the Malfunction Indicator Lamp (MIL).
- DTC P0742 will be stored in PCM memory.
- Freeze shift adapts from being updated.
- PCM commands the TCC on.

Condition For Clearing DTC
- The PCM will turn the MIL off after DTC P0742 passes condition test. This DTC passes when all conditions for setting the DTC are true, (except TCC release switch is open when TCC is commanded off for three seconds) for three consecutive ignition cycles.
- History DTCs can be cleared by using a Scan Tool.

Diagnostic Aids
- Rapid fluctuation in line pressure could set a DTC P0742.
- Check for a possible pressure regulator problem.
- Check for possible high or low line pressure.
- Inspect the wiring for poor electrical connections at the PCM and at the transmission 20-way connector. Look for possible bent, backed out, deformed or damaged terminals. Check for weak terminal tension as well. Also check for chafed wires that could short to bare metal or other wiring. Inspect for broken wire inside the insulation.
- If diagnosing for a possible intermittent short or open condition, move or massage the wiring harness while observing test equipment for a change.

Test Description
The numbers below refer to the step numbers on the diagnostic chart.
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 502 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.

DTC P0742 - Torque Converter Clutch Circuit Stuck On





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