Powertrain, generic · Transmission

P0743 Torque Converter Clutch Circuit Electrical

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

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.

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

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)

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–1,200
Time1–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

torque converter clutch solenoidtorque convertertransmission valve bodytransmission control module

Related codes

P0740P0741P0742P0744P2763P2764

References: saabwisonline.com, saabwisonline.com, saabwisonline.com, gsi.ext.gm.com.