P0743Torque Converter Clutch Circuit Electrical
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- The torque converter clutch (lock-up) connects pump and turbine mechanically; a solenoid – on/off, pulse-width modulated or proportional – moves a control valve in the valve body. Slip is engine speed minus turbine speed. Manufacturers do not use P0740–P0744 uniformly: Ford uses P0740 for open, P0742 for short to ground and P0744 for short to power, and reports stuck on as P2758. P0743 is the collective electrical code for the converter clutch solenoid circuit – open, short to ground or to positive – detected by terminal voltage, driver feedback or current. Subaru flags it after 0.14 s and lights the MIL after two trips, Saab's 9-3 of 2003 above 1356 mA for 500 ms, Allison after 1.5 s; older Ford transmissions also use it. The clutch is switched off; Saab's Aisin boxes go into limp mode, Subaru does not.
- What you may notice
- Check engine light or transmission warning
- No lock-up: engine speed about 100–300 rpm higher when cruising
- Limp mode on some makes (Saab/Aisin)
- Likely causes
- LikelyTransmission harness or pass-through connector (corrosion, chafing, oil in connector)
- LikelySolenoid coil open or shorted
- PossibleInternal harness or mechatronic unit
- RareDriver stage in the transmission or engine module
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €80 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.