Transmission Control System

TCC Solenoid:

PURPOSE
The Torque Converter Clutch (TCC) system is designed to eliminate power loss by the converter (slippage) thus increasing fuel economy. By locking the converter clutch, a more effective coupling to the flywheel is achieved. The converter clutch is operated by an Powertrain Control Module (PCM) controlled solenoid.

OPERATION
Engagement of the TCC is accomplished by a solenoid operated valve within the transaxle. The solenoid is activated when an internal switch in the PCM is grounded. Although the PCM may command the TCC "ON," the converter clutch will not apply until internal transaxle fluid pressure requirements are met.

Before the PCM activates the TCC apply solenoid, several inputs must be monitored.

Vehicle speed
Must be above (35 mph with A/C "OFF," 44 mph with A/C "ON") before the TCC can be applied.

Coolant temperature
The engine coolant temperature must be above 20°C (68°F) before the TCC can be applied.

Throttle Position (TP) sensor
After the TCC is applied, during low engine load condition, the PCM uses data from the TP sensor to release the clutch when the throttle is being opened or closed faster than a calibrated rate.

CIRCUIT DESCRIPTION
The 12 volt power supply for the TCC solenoid in the transaxle is provided through a normally closed switch located on the brake pedal linkage. When the brake pedal is depressed (switch open) the power supply to the TCC solenoid is interrupted and the TCC is disengaged regardless of other conditions. A 3rd gear apply switch (closed in 3rd gear) is placed between the solenoid and the TCC control driver in the PCM. This switch will prevent TCC engagement until the transaxle is in 3rd gear.

When the brake pedal is not depressed (switch closed) and the transaxle is in 3rd gear (3rd gear switch closed), battery voltage will be fed to the TCC solenoid. If the PCM has determined that conditions are correct, the circuit from the TCC solenoid will be completed to ground through the PCM and the TCC solenoid will be activated.

DIAGNOSIS
The diagnosis of the TCC system is covered in CHART C-8A. If the PCM detects a Vehicle speed Sensor (VSS) input problem in the system, a Diagnostic Trouble Code (DTC) 24 should set. In this case, refer to DTC 24 chart.

If the PCM doesn't enable the TCC when commanded but the TCC will enable when commanded with the Tech 1, sensors such as Engine Coolant Temperature (ECT), VSS and Throttle Position (TP) sensor should be checked.