Transmission · Powertrain · generic (SAE-defined)
P0740: Torque Converter Clutch Solenoid Circuit/Open
P0740 means the transmission control module has detected an open or otherwise faulty electrical circuit for the torque converter clutch solenoid, so it cannot reliably command converter lockup.
Standard title per SAE J2012 / ISO 15031-6 · Updated 2026-11-07 · By CarWhere Research
How P0740 sets
The powertrain or transmission control module (PCM/TCM) energizes the torque converter clutch (TCC) solenoid to lock the converter at cruising speeds. The module monitors the solenoid control circuit and sets P0740 when the circuit voltage or current does not match what it expects for the commanded state, such as an open circuit. The exact electrical limits and enable conditions are manufacturer-specific.
Common causes of P0740
Roughly most likely first; the actual cause depends on the vehicle and needs testing to confirm.
- Failed TCC solenoid with an open winding
- Damaged or corroded transmission harness connector
- Broken or chafed wire in the TCC solenoid circuit
- Faulty internal transmission wiring harness or pass-through connector
- Blown fuse or poor power feed to the solenoid circuit
- Fault in the PCM/TCM driver circuit (less common)
P0740 symptoms
- Check engine light on
- Torque converter does not lock up at highway speed
- Reduced fuel economy
- Higher engine speed than normal while cruising
- Transmission fluid running hotter than usual
How P0740 is diagnosed
- Scan for all codes and review freeze frame data; address any voltage or other transmission codes first.
- Inspect the transmission connector and harness for damage, fluid intrusion, corrosion, or bent pins.
- Check the fuse and power feed that supply the solenoid circuit.
- Measure TCC solenoid resistance at the transmission connector and compare to the factory specification.
- If resistance is out of range, check the internal harness before condemning the solenoid.
- Command the TCC on and off with a bidirectional scan tool and watch for a response in engine speed or slip data.
Typical fixes for P0740
- Repair damaged wiring or a corroded connector
- Replace the torque converter clutch solenoid
- Replace the internal transmission harness or pass-through connector
- Replace a blown fuse after finding the cause
- Repair or replace the PCM/TCM if its driver is confirmed faulty
Replace parts only after testing confirms the cause — a code names the circuit or condition that failed a check, not necessarily the faulty part. We don’t publish per-repair prices; for what households actually spend on upkeep, see car repair costs.
Manufacturer notes
Some older definitions read 'Torque Converter Clutch Circuit Malfunction'. Definitions can vary by manufacturer; check factory service information.
Related codes & warning lights
P0740 FAQ
What does code P0740 mean?
P0740 means the transmission control module has detected an open or otherwise faulty electrical circuit for the torque converter clutch solenoid, so it cannot reliably command converter lockup. The standard definition is "Torque Converter Clutch Solenoid Circuit/Open."
Can I drive with a P0740 code?
Usually yes for short trips, since the transmission typically still shifts. Without converter lockup, fuel economy drops and fluid runs hotter, so have it diagnosed within days and avoid towing or long highway runs.
Does P0740 mean my torque converter is bad?
Not usually. P0740 points to the electrical circuit that controls the clutch, so wiring, connectors, or the solenoid itself are far more likely than a failed converter.
Why did my gas mileage drop with P0740?
When the converter cannot lock, some engine power is lost to fluid slip in the converter. That slip raises engine speed at cruise and costs fuel.
Keep researching
More transmission codes
Sources
- SAE J2012 — Diagnostic Trouble Code Definitions (standard code titles)
- ISO 15031-6 — Road vehicles: communication between vehicle and external equipment for emissions-related diagnostics, Part 6: Diagnostic trouble code definitions
- U.S. EPA — Vehicle Emissions Inspection and Maintenance (I/M) programs
- U.S. EPA, 40 CFR 86.1806-17 — Federal onboard diagnostics requirements for light-duty vehicles
General information written by CarWhere Research, not a diagnosis of your vehicle. Manufacturers can add their own sub-definitions and test conditions; confirm with the factory service information for your year, make and model. Before paying for a repair, check NHTSA for open recalls and your warranty booklet: federal law requires an emissions warranty on major emission-control parts such as the catalytic converter and engine computer.