P0742

P0742 - TCC SYSTEM STUCK ON





The Torque Converter (TCC) clutch solenoid is a pulse width modulated solenoid. When vehicle operating conditions are met for TCC application, the PCM/TCM begins the duty cycle at approximately 42%. The PCM/TCM then increases the duty cycle up to 90% in order to achieve full TCC apply. When the TCC solenoid 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 TCC release switch is a normally closed switch. It signals the PCM/TCM the TCC is released. Torque converter release fluid pressure acts on the switch contact, opening the circuit. When the voltage on the circuit is high, the PCM/TCM recognizes the TCC is no longer engaged.
When the PCM/TCM detects the TCC solenoid release switch is closed when the TCC is commanded OFF, then DTC P0742 sets.

DTC PARAMETERS
- Engine is running
- TP angle is greater than 8%
- TFT is between 21° C (70° F) and 130° C (266° F)
- Engine torque greater than 40 ft. lbs.
- Gear ratio 3rd and 4th
- TCC is commanded OFF
- No engine torque default
- Time since last manual range change greater than 6 seconds
- No ISS, OSS, TCC release switch, TCC electrical, TCC stuck ON, TFP or TP sensor DTCs have been set
P0721 is a (type A) DTC.

DIAGNOSTIC AIDS
Inspect and repair as necessary:
- TCC solenoid exhaust restricted
- TCC solenoid filter plugged
- TCC control valve stuck in the released position
- TCC regulated apply valve stuck in the released position
- TCC feed limit valve stuck Pressure regulator valve stuck
- TCC fluid circuit leaks
- TCC release switch for damaged or leaking seal, debris in switch, damaged switch contacts, stuck switch contacts.