What P0740 means
At cruise, a clutch inside the torque converter locks engine to transmission directly, eliminating the converter's fluid slip for economy. P0740 means the circuit controlling that lockup clutch is faulty — the computer commands lockup and the electrical side doesn't cooperate.
What you’ll notice
- RPM slightly high and 'soft' at highway cruise
- Fuel economy down noticeably
- Sometimes shudder as lockup tries and fails
- Running warmer on long drives
Likely causes and repair cost
Broad US independent-shop bands, parts and labour.
Can you drive with P0740?
Yes, with a heat note: an unlocked converter sheds its slip as fluid heat, so long highway pulls and towing run the transmission hotter than designed. Around town it's mostly a fuel-economy tax.
The misdiagnosis to avoid
Living with it because around-town driving feels fine. The unlock tax compounds: a few hundred RPM of permanent highway slip is heat, and heat is the primary killer of transmission fluid and clutches. The solenoid-level fix now is cheap insurance against fluid cooked into the expensive kind of failure.
Describe what it’s doing in your own words and the symptom checker gives you a safe-to-drive verdict, ranked causes with costs, and notes to take to the shop — free, no sign-up.
Read the code yourself
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How much fuel is the dead lockup costing me?
Typically several percent at highway speeds — lockup exists because converters waste meaningful energy as heat at cruise. Drivers who fix a long-standing P0740 often report highway economy quietly returning to numbers they'd forgotten the car could do.
What's the difference from P0741?
P0740 is electrical — the circuit misbehaves. P0741 is performance — the circuit works, lockup is commanded, and slip is still measured across the converter: the clutch itself can't hold. Same subsystem, but P0741 points harder at the converter as hardware, and its repair conversation is bigger.