The torque converter clutch locks the engine directly to the transmission at cruising speed for better efficiency (instead of running through the fluid coupling). This code means that lock-up clutch isn't engaging when it should — the transmission is stuck relying on the less efficient fluid coupling all the time.
Symptoms
- Slightly higher engine RPM than normal at steady highway speed
- Worse fuel economy on the motorway specifically
- A subtle "slipping" feeling under light steady-throttle cruising
- Transmission may run slightly hotter than normal over long drives
Likely causes
- Low or degraded transmission fluid — often the simplest and most common cause
- A failing torque converter clutch solenoid
- Internal wear in the torque converter itself
- A wiring or connector fault to the solenoid
How to diagnose it
- Check transmission fluid level and condition first — this alone resolves many cases
- Test the torque converter clutch solenoid's resistance and operation with a scan tool
- If fluid and solenoid both check out, internal torque converter wear becomes the more likely (and more expensive) cause
Typical fixes & cost
- Transmission fluid and filter service100–300 EUR
- Replace the torque converter clutch solenoid150–400 EUR
- Replace the torque converter (only if confirmed worn internally)600–1800 EUR
Code names are compiled from open/standardized SAE and ISO references. Explanations, symptoms, causes and fixes are original. Covers generic (P0/C0/B0/U0) codes only — manufacturer-specific codes are planned for a future update.
AS
Reviewed by Artyom SemenovAutomotive Editor · Fact-checked by Yauheni Kapliarchuk, Editor-in-Chief