P0740: Torque Converter Clutch Circuit/Open
The transmission computer has found an electrical problem in the torque converter clutch solenoid circuit, so the converter may not lock up.
What P0740 means
A torque converter connects the engine to the transmission through fluid. At cruising speeds, a clutch inside it locks the engine and transmission together to stop slipping, improve fuel economy and lower fluid temperature. The transmission computer controls that lockup with a solenoid. P0740 means the computer has found the solenoid circuit open or electrically faulty. RepairPal lists a defective lockup solenoid, a defective coolant temperature sensor, a defective converter clutch, a valve body problem and dirty fluid as causes, and notes symptoms such as not shifting into the highest gear at freeway speed, lower fuel economy and stalling when stopping after freeway driving. The coolant sensor matters because many computers will not lock the converter until the engine is warm. Shops measure solenoid resistance through the transmission connector, check wiring, and command the solenoid with a scan tool. On many transmissions the solenoid is reachable after removing the pan.
Common symptoms
- Check engine light on
- Higher RPM at highway speed
- Worse fuel economy
- Transmission running hot
- Stalling when coming to a stop on some vehicles
Most common causes
- Failed torque converter clutch solenoid
- Open or shorted wiring to the solenoid
- Corroded transmission connector
- Faulty engine coolant temperature sensor input
- Dirty fluid affecting the valve body
- Transmission control module fault
What to check yourself first
Check the transmission connector for oil leaks or corrosion. Note your RPM at a steady 60 mph; if it is higher than usual, the converter may not be locking. Check fluid level and condition.
Typical fixes and what they cost
| Fix | Typical cost | Note |
|---|---|---|
| Transmission filter and fluid service | $621-$785 | The TCC solenoid is often inside the pan and replaced during a pan and filter service. |
| Electrical diagnosis to find a wiring or connector fault | $122-$179 | For wiring or connector faults. |
| Transmission fluid change | $294-$356 | Low or burnt fluid causes many transmission codes. Check the correct fluid type for your transmission. |
| Replace transmission control module | $929-$1,006 | Only if the module driver is proven faulty. |
Typical US price ranges for parts and labor, not quotes. Your shop should confirm the cause with a diagnostic before replacing parts.
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Related codes
- P0741 Torque Converter Clutch Circuit Performance/Stuck Off
- P0700 Transmission Control System (MIL Request)
- P0711 Transmission Fluid Temperature Sensor "A" Circuit Range/Performance
- P0730 Incorrect Gear Ratio
- P0118 Engine Coolant Temperature Sensor 1 Circuit High