What it means
A fault has been detected in the torque converter clutch circuit. This code does not by itself identify whether the fault is electrical or related to clutch operation.
At a glance
- Usually lights the check-engine light
How it works
The torque converter clutch (TCC) is a friction clutch that can couple the engine and transmission more directly during suitable driving conditions. The controller monitors the TCC electrical circuit and clutch response; P0740 flags a circuit or operation malfunction, but does not alone prove whether the solenoid, wiring, fluid, or clutch is at fault.
Common causes
Most likely first.
- TCC solenoid failed
- Transmission fluid low or burnt
- Wiring fault to solenoid
Symptoms
- Check engine or transmission warning light on
- Torque converter lockup may not operate as expected
How to diagnose it
- Record freeze-frame data and check when the TCC was commanded, along with engine and transmission speeds and any related transmission codes.
- Inspect the TCC solenoid wiring and connectors for chafing, corrosion, loose terminals, or fluid intrusion.
- Check transmission-fluid level and condition and look for leaks, following the manufacturer's procedure.
- Use a scan tool to compare the TCC command with the observed engine-to-transmission speed difference under the conditions in the freeze-frame.
- Test the TCC circuit and solenoid, then check hydraulic control and converter operation using the manufacturer's diagnostic procedure.
Common fixes
- Repair damaged TCC wiring or corroded or loose connector terminals.
- Correct low fluid and repair any leak using the specified fluid and procedure.
- Replace a TCC solenoid confirmed faulty by circuit testing.
- Repair a valve-body or hydraulic-control fault identified during diagnosis.
- Repair or replace the torque converter only if testing confirms a converter fault.
Can I keep driving?
If the vehicle still shifts normally, limit strenuous driving and arrange diagnosis soon; avoid towing or heavy loads until the TCC fault is understood. Stop if the transmission overheats, slips, or develops severe shift problems.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.