P0740
Torque Converter Clutch Circuit/Open
Transmission / torque converter
Generic OBD-II
Medium
What it means
P0740 means the transmission control module found an open or fault in the torque converter clutch (TCC) circuit, so the converter clutch can't lock up. Without lockup the engine turns faster at cruising speed, fuel economy dips, and the transmission runs hotter. It's usually electrical — a bad solenoid or wiring — rather than a broken transmission.
Medium
Can I keep driving? Drivable, but with no converter lockup the engine runs at higher rpm and the transmission runs hotter — avoid long highway trips until it's fixed.
Common symptoms
What you'll notice
- Check-engine light on
- Higher-than-normal engine rpm at steady cruising speed (no lockup)
- Slightly reduced fuel economy
- Transmission running hotter than usual
Common causes
Most likely first
- Faulty torque converter clutch (TCC) solenoidLikely
- Open or damaged wiring / connector in the TCC circuitCommon
- Loose or corroded electrical connectionsCommon
- Low or dirty transmission fluid affecting solenoid operationLess often
- Failed transmission control module (TCM)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and confirm the code; check for other transmission codes.
- Inspect the TCC solenoid connector and wiring for opens or corrosion.
- Check transmission fluid level and condition.
- Measure the TCC solenoid resistance and replace it if open or out of spec.
- If the solenoid and wiring are good, evaluate the TCM. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0740?+
For short trips, yes. The converter clutch just isn't locking up, so avoid sustained highway driving until it's fixed to keep the transmission from overheating.
Can I just clear P0740?+
You can, but it returns until the solenoid or circuit fault is repaired — the TCM checks the TCC circuit continuously.
Related codes
Often seen with P0740
Read & clear P0740 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX