P0742
Torque Converter Clutch Circuit Stuck On
If your vehicle's onboard computer has flagged the diagnostic trouble code P0742, it refers to a detected anomaly regarding "Torque Converter Clutch Circuit Stuck On". This systemic engine fault needs a targeted check before symptoms expand.
Driver's Summary
When your OBD2 scanner shows P0742, the engine control module has flagged an issue specifically related to torque converter clutch circuit stuck on. In practice, this fault causes engine stalls when coming to a stop, harsh engagement into gear. Given the high severity of this code, continuing to drive risks significant mechanical damage. Have it diagnosed immediately.
Symptoms
Engine stalls when coming to a stop, harsh engagement into gear
Common Causes
- TCC solenoid stuck open
- Debris in valve body holding TCC valve
- Failed torque converter
- Short to ground in TCC wiring
How to Fix
- 1 Replace TCC solenoid
- 2 Remove and clean transmission valve body
- 3 Replace torque converter
- 4 Repair shorted wiring
Technical Explanation
The ECM detects code P0742 by continuously monitoring the relevant sensor circuit against calibrated threshold values stored in its non-volatile memory. The TCM compares the ratio between input turbine speed sensor and output speed sensor readings against the expected gear ratio stored for each commanded gear position. A deviation greater than a few percent indicates clutch slippage, solenoid malfunction, or internal mechanical failure. The fault remains stored in memory even after the MIL is cleared; it becomes a confirmed DTC after failing two consecutive drive cycles, and the PCM logs a freeze frame record of the engine's exact operating state at the moment of detection.
Is It Safe to Drive?
With P0742 active, your engine or transmission is not operating within design parameters. Short-term driving may seem fine, but internal damage is accumulating — particularly to tcc solenoid stuck open.
Mechanic's Pro Tip
For P0742, test the solenoid's coil resistance with a multimeter before ordering parts — most solenoids should read between 14 and 40 ohms; an open (infinite resistance) or short (near zero) confirms it's failed electrically. Also verify the PCM is commanding the solenoid by backprobing the connector with a test light during the relevant operating condition — if there's no command signal, the fault is in the PCM or wiring, not the solenoid itself.
Valve body clean/solenoid: $300 - $800; Torque converter: $1,200 - $1,800