Sticking or faulty torque converter clutch solenoid or lock-up control solenoid; Contaminated, degraded or incorrect level of transmission fluid blocking valve movement; Worn, sticking or contaminated valve body components such as the lock-up control valve; Wiring fault, short to power or poor connector contact in the solenoid circuit; Internal torque converter fault, such as a clutch that is stuck or has failed mechanically; Faulty input or output speed sensor giving an incorrect slip reading; Transmission control module fault or outdated software where a known issue exists.

P0742

Torque Converter Clutch Circuit Stuck On.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
7: AreaTransmission
42: FaultThe specific fault in that area

What it means

P0742 means the transmission control module has detected that the torque converter clutch is staying locked (engaged) when it has commanded it to release, or that the engine-to-turbine speed relationship shows no slip when slip is expected. The module compares engine speed with transmission input speed and finds the converter locked up in conditions where it should be unlocked. The exact monitoring strategy and the conditions for setting the code vary by manufacturer and transmission.

Symptoms

Engine stalls or nearly stalls when braking to a stop or when pulling up in gear
Shuddering or juddering at low speed as if the clutch is being dragged
Rough or unstable idle when in Drive with the brakes applied
Harsh or jerky shifts or a feeling of the car being held back
Malfunction indicator lamp on, possibly with transmission warning light or limp mode
Poorer fuel economy

Possible causes

Sticking or faulty torque converter clutch solenoid or lock-up control solenoidlikely
Contaminated, degraded or incorrect level of transmission fluid blocking valve movementlikely
Worn, sticking or contaminated valve body components such as the lock-up control valvepossible
Wiring fault, short to power or poor connector contact in the solenoid circuitpossible
Internal torque converter fault, such as a clutch that is stuck or has failed mechanicallypossible
Faulty input or output speed sensor giving an incorrect slip readingpossible
Transmission control module fault or outdated software where a known issue existsrare

How to diagnose

Read all stored and pending codes and freeze frame data, noting vehicle speed, gear, engine speed and fluid temperature when the code set
Check the transmission fluid level and condition, and compare with the manufacturer's specification for your model, as the correct check procedure varies
Check for related codes such as speed sensor or solenoid circuit faults and deal with those first
Inspect the transmission wiring harness and connector for chafing, corrosion, fluid ingress or damaged pins
Measure the resistance of the lock-up solenoid and check its supply and control signals against specification
Use live data to compare engine speed and turbine speed, and watch the commanded lock-up state against actual slip
Road test with data logging to see whether the converter stays locked when commanded off, such as when slowing to a stop
Check for any manufacturer service bulletins or software updates relating to this code for your model and transmission

How to fix

Repair or replace damaged wiring or connectors in the solenoid circuit
Replace the torque converter clutch solenoid if it is faulty or sticking
Correct the fluid level, or change the fluid and filter using the specified type if it is degraded or contaminated
Overhaul or replace the valve body or worn valve components as required
Replace or overhaul the torque converter if it is found to be mechanically stuck
Replace a faulty speed sensor, or update the control module software if a known calibration fault applies

Can I keep driving?

Medium severity

The car can usually be driven short distances, but stalling when stopping and continued converter clutch drag can cause overheating and transmission damage, so get it checked soon. Avoid long journeys, and stop driving if the car stalls repeatedly or goes into limp mode.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.