P0740: Torque converter clutch circuit malfunction
The gearbox has found an electrical fault in the control of the torque converter clutch, which locks the engine to the automatic gearbox at cruising speed to save fuel.
Updated
What P0740 means
An automatic gearbox is driven by the engine through a torque converter, a fluid coupling that always slips a little. To save fuel at cruising speed, a clutch inside it locks the engine to the gearbox: the torque converter clutch. A solenoid in the gearbox, controlled by the gearbox module, engages it.
P0740 means the gearbox has found an electrical fault in that solenoid’s circuit.
P0741 to P0744: stuck off, stuck on, electrical, intermittent
P0741 means the clutch doesn’t lock, or slips when locked: the engine revs a little higher at a steady speed, fuel use goes up and the gearbox oil runs hotter. P0742 means it stays locked: like stopping a manual car without pressing the clutch, the engine can stall when the car stops. P0743 and P0744 are electrical faults, constant or now and then.
P0741: Torque converter clutch circuit performance or stuck off
The torque converter clutch doesn’t lock up when the gearbox tells it to, or it slips when locked.
Common causes: faulty torque converter clutch solenoid or valve body, low, old or contaminated gearbox oil, worn torque converter.
P0742: Torque Converter Clutch Circuit Stuck On
The torque converter clutch stays locked when it should release. The engine can stall when the car stops.
Common causes: torque converter clutch solenoid stuck on, or a short in its circuit, sticking valve in the valve body, low, old or contaminated gearbox oil.
P0743: Torque Converter Clutch Circuit Electrical
P0744: Torque Converter Clutch Circuit Intermittent
Can I keep driving?
Drive gently
Drive gently and have it checked soon. If the converter clutch stays locked, the engine can stall when you stop, and steering and braking then get much heavier; if it doesn’t lock, the gearbox oil runs hotter and wears faster. If the engine stalls when you stop, or the gearbox slips or shifts erratically, don’t drive on: have it recovered.
General guidance based on the code alone, not on the car’s actual condition. If in doubt, stop and ask a mechanic.
If the engine stalls when you come to a stop, the clutch is probably staying locked: don’t drive on, have the car recovered. Read My Car shows codes from the gearbox module next to the engine’s, where the car shares them over generic OBD2.
Symptoms
- Shudder or judder at a steady speed, as the clutch tries to engage.
- A higher engine speed than usual when cruising, and higher fuel use.
- The engine stalls when the car stops (clutch stuck on).
- On some cars, the gearbox goes into limp mode.
Common causes
- Faulty torque converter clutch solenoid. The most common cause. On many gearboxes it sits in the valve body, inside the gearbox.
- Wiring or connector fault, often inside the gearbox. Wiring inside the gearbox, and its connector on the case, can fail too.
- Low, old or contaminated gearbox oil. Dirty oil can make the solenoid stick.
Typical fixes
- Read all codes, including any the gearbox module reports.
- Have the gearbox oil level and condition checked, as the service information for your gearbox describes. An oil change sometimes helps.
- Have the solenoid and its circuit tested, and the solenoid replaced if it’s faulty.
- If the clutch slips mechanically, the torque converter may need replacing.
Questions
Can I drive with P0740?
Gently, and have it checked soon. If the engine stalls when you stop, or the gearbox slips or shifts erratically, don’t drive on: have it recovered. A stuck clutch can stall the engine, and a slipping one makes the gearbox oil run hotter.
Why does my car stall when I stop?
If the torque converter clutch stays locked (P0742), the engine is still connected to the wheels when you stop, like a manual car with the clutch pedal up, so it stalls. Don’t drive on: have it checked.