P0742: Torque Converter Clutch Circuit Stuck On
The torque converter clutch stays locked when it should be released.
High risk
The engine may stall when you stop. Have it checked soon.
Short answer · Can I keep driving with P0742?
With caution. If the clutch stays locked, the engine can stall when you brake to a stop, like a manual car with the clutch engaged. Have it checked soon.
What does P0742 mean?
P0742 means the transmission control unit sees engine and turbine speeds matching when the converter clutch should be open. A solenoid stuck on, a sticking valve in the valve body, dirty fluid or a short in the solenoid circuit are typical causes.
What the car does when the code is set
The check engine or transmission warning comes on. You may notice slipping, flare when shifting, late engagement or the transmission staying in one gear.
How the system works
In each gear, an automatic transmission has a known ratio between its input and output speed. The transmission control unit compares the measured speeds with the expected ratio for the gear it has selected. If they do not match, a clutch or band is slipping, a shift has not been completed, or a speed signal is wrong. To protect the transmission, the control unit may lock it in one gear (limp mode) until the fault is cleared.
Common symptoms
Possible causes
Listed without ranking. The cause on your car depends on make, engine and mileage — see the maker notes below.
- Low or degraded transmission fluidClutches slip if the pressure is low.
- Worn clutches or bandsInternal wear lets the transmission slip.
- Faulty shift solenoids or valve bodyPressure is not controlled correctly.
- Speed sensor problemWrong speed readings give a wrong ratio calculation.
How it is diagnosed
- Check the fluidCheck level, colour and smell. Burnt fluid points to internal wear.
- Read gear ratio dataLive data shows which gear the ratio does not match.
- Check solenoids and sensorsTest them electrically and check other transmission codes.
- Pressure testA workshop measures line pressure to find internal problems.
Questions about P0742
Why does the engine stall with P0742?
A locked converter connects the engine directly to the gearbox. When the car stops, the engine is forced to stop too, unless the clutch releases.
Will a fluid change fix it?
Only if old or low fluid is the cause. If clutches are worn, new fluid may help for a short time only.