P0740: Torque Converter Clutch Solenoid Circuit/Open
The transmission control unit has detected an open circuit or another electrical fault in the torque converter clutch solenoid circuit.
Normal risk
Usually drivable. Fuel use and transmission temperature may rise. Have it checked soon.
Short answer · Can I keep driving with P0740?
Usually yes. The converter clutch will not lock, so engine speed is higher at steady cruising and fuel use rises. Have it checked soon.
What does P0740 mean?
P0740 means the transmission control unit cannot drive the solenoid that locks the torque converter clutch, because the circuit is open or the current is not plausible. A failed solenoid, a broken wire, a corroded connector or a fault in the internal harness are typical causes.
What the car does when the code is set
The check engine light comes on. Depending on the transmission fault, shifting may be normal, harsh or delayed, or the transmission may stay in one gear (limp mode).
How the system works
An automatic transmission has its own control unit that reads speed sensors, the selector position and pressure sensors, and controls shifting through solenoids. When it detects a fault that can affect emissions, it asks the engine control unit to light the check engine lamp. Because the engine control unit stores a code for that request, a basic scanner often shows only this code, while the detailed code stays in the transmission control unit.
Common symptoms
Possible causes
Listed without ranking. The cause on your car depends on make, engine and mileage — see the maker notes below.
- Fault in the transmission control systemThis code only reports that the transmission control unit has stored its own fault.
- Low or old transmission fluidOften found together with shifting codes.
- Sensor or solenoid faultSpeed sensors, pressure solenoids and wiring.
- Communication problemBetween the engine and transmission control units.
How it is diagnosed
- Read the transmission control unitUse a scan tool that reads the transmission module: the real cause is stored there.
- Check the fluidCheck level and condition as the service data describes.
- Follow the specific codeDiagnose the code from the transmission module.
- Clear and test-driveClear codes from both modules and test-drive.
Questions about P0740
What is the difference between P0740 and P0741?
P0740 is an electrical fault in the solenoid circuit. P0741 means the circuit seems fine but the clutch does not lock as commanded, which points more to fluid, valve body or clutch wear.
Why does my basic scanner only show this code?
Many simple scanners read only the engine control unit. A scanner that reads the transmission module shows the real fault code.
Is P0700 a transmission failure?
Not necessarily. It only reports that the transmission control unit stored a fault. The real code there shows what is wrong.