P0743 GMC Torque Converter Clutch Circuit Electrical

Possible causes

– Faulty torque converter clutch solenoid valve
– Torque converter clutch solenoid valve harness is open or shorted
– Torque converter clutch solenoid valve circuit poor electrical connection
– Low transmission fluid level
– Dirty transmission fluid

Tech description

This is an electrical problem code. Could be a problem to the harness to the Torque Converter Clutch (TCC) solenoid, the TCC solenoid connector or the TCC solenoid it self.

What about the obd code?

By performing a voltage drop test, the Engine Control Module (ECM) detects that the Torque Converter Clutch (TCC) solenoid circuit is open or shorted.

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

P0743 GMC Description

The Torque Converter Clutch (TCC) solenoid valve is activated, with the gear in D4, by the Transmission Control Module (TCM) in response to signals sent from the vehicle speed and the Engine Control Module (ECM). Lock-up piston operation will then be controlled. When the torque converter clutch solenoid valve is activated, the torque converter lockup clutch will engage creating a 1 to 1 RPM ratio between the transmission input shaft and the rotational speed of the torque converter.

Lock-up operation, however, is prohibited when A/T fluid temperature is too low.

When the accelerator pedal is depressed (less than 2/8) in lock-up condition, the engine speed should not change abruptly. If there is a big jump in engine speed, there is no lock-up.