Fault code P0740 – a step-by-step guide to diagnosing and fixing it

Error code P0740 is displayed and the check engine light is on - what does this mean?

The OBD/EOBD system has detected a fault in the torque converter lock-up clutch of the automatic transmission. This DTC P0740 indicates that the electronic control of the torque converter lock-up clutch is not functioning properly. This fault code can have slightly different meanings for different manufacturers, but always affects the automatic transmission.

What causes can this error code have?

• Defective torque converter lock-up clutch
• Worn or damaged solenoid valves in the transmission control unit
• Low transmission oil level or contaminated ATF oil
• Defective torque converter
• Damaged wiring to the transmission control unit
• Faulty transmission control unit (TCM/PCM)
• Clogged transmission oil filter
• Mechanical damage in the automatic transmission

What symptoms occur in parallel with fault code P0740?

• Shifting problems: The automatic transmission shifts jerkily or irregularly between gears
• Increased fuel consumption: The engine operates more inefficiently because the torque converter lock-up is not working
• Transmission overheating: The transmission oil becomes unusually hot while driving
• Loss of power: Noticeable reduction in engine performance, especially at higher speeds
• Engine stuttering: Irregular engine running at idle or at constant speed

What can cause this error code?

• Various repair approaches are possible to rectify error code P0740, depending on the underlying cause.
• Change the transmission oil with high-quality ATF oil and replace the transmission oil filter
• Replace or clean the solenoid valves of the torque converter lock-up in the transmission control unit
• Replace the entire torque converter if there are mechanical defects
• Diagnose transmission control unit (TCM) and replace or reprogram if necessary
• Check and repair wiring and plug connections to the transmission control unit
• Overhaul or replace the entire automatic transmission if there is serious internal damage