Dirty transmission fluid
Low transmission fluid level
Faulty Torque Converter Clutch (TCC) Solenoid Valve
Torque Converter Clutch Solenoid Valve harness is open or shorted
Torque Converter Clutch Solenoid Valve circuit poor electrical connection
Engine Light ON (or Service Engine Soon Warning Light)
The Torque Converter Clutch (TCC) is designed to increase efficiency by mechanically coupling the engine to the transmission. The 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. The 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. By performing a voltage drop test, the ECM detects that the Torque Converter Clutch (TCC) solenoid circuit is open or shorted and sets the Diagnostic Trouble Code (DTC).