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.
Medium severity. Can I keep driving?Drive gently to a repair shop. If it slips, you hear clunks, or it loses its gears, do not keep driving.
Symptoms
- 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)
Most likely causes
- Transmission harness or pass-through connector (corrosion, chafing, oil in connector)
- Solenoid coil open or shorted
- Internal harness or mechatronic unit
- Driver stage in the transmission or engine module
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It can trigger limp mode.
- It affects emissions.
What each character of P0743 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 7: Transmission
- 43: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0743?
Drive gently to a repair shop. If it slips, you hear clunks, or it loses its gears, do not keep driving.
What causes code P0743?
The most common causes are: transmission harness or pass-through connector (corrosion, chafing, oil in connector); solenoid coil open or shorted; internal harness or mechatronic unit.
Related codes
- P0740Torque Converter Clutch Circuit/Open
- P0741Torque Converter Clutch Circuit Performance/Stuck Off
- P0742Torque Converter Clutch Circuit Stuck On
- P0744Torque Converter Clutch Circuit Intermittent
- P2763Torque Converter Clutch Pressure Control Solenoid Control Circuit High
- P2764Torque Converter Clutch Pressure Control Solenoid Control Circuit Low
Sources
- saabwisonline.com: dtc p0743 torque converter clutch circuit electric
- saabwisonline.com: p0743
- saabwisonline.com: p0743 01
- gsi.ext.gm.com: 2006trans9
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.