Torque Converter Clutch Solenoid: Testing and Inspection

Transaxle Mode Switch And Shift Solenoid Circuit Diagram:

CIRCUIT DESCRIPTION AND SOLENOID OPERATION

The purpose of the Torque Converter Clutch feature is to eliminate the power loss of the torque converter when the vehicle is in a cruise condition. This allows the convenience of the automatic and the fuel economy of a manual transaxle. Two PCM controlled solenoids, located inside the transaxle, regulate fluid pressure to the torque converter clutch. One solenoid (the TCC solenoid) provides fluid pressure to the TCC, the other solenoid (the Pulse Width Modulated or PWM solenoid), regulates pressure for a smooth apply.

The solenoids get battery power when the ignition is turned "ON", and become energized when the PCM completes the circuit to ground. When the TCC solenoid coil is activated ("ON,") fluid pressure applies the torque converter clutch, making a straight mechanical coupling between the engine and transmission. When the TCC solenoid is deactivated, fluid pressure to the TCC is released and the torque converter clutch disengages, allowing the torque converter to operate in the conventional manner (fluid coupling between engine and transaxle).


TCC will engage when:

^ Engine warmed up.
^ Vehicle speed above a calibrated value (about 47 mph - 72kph).
^ Throttle position sensor output not changing, indicating a steady road speed.
^ Brake switch closed.

TEST DESCRIPTION

Chart C-8B, Transaxle Mode Switch Diagnosis (2 Of 4):

Numbers below refer to circled numbers on the diagnostic chart.

1. This test checks the operation of the TCC soolenoid and circuit.
2. This checks the TCC control driver in the PCM. Repeat output test as in previous step. Test light should be "OFF" when TCC is commanded "OFF", and should be "ON" when TCC is commanded "ON".
3. This checks for battery power to the TCC solenoid connector. If there is no power at terminal "A" of connector, check 10A (INDIC) fuse.
4. This test confirms whether or not the PCM can complete the circuit to ground, to turn the TCC solenoid "ON".

DIAGNOSTIC AIDS:
The "Scan" tool only indicates when the PCM has turned "ON" the TCC driver and this does not confirm that the TCC has engaged. To determine if TCC is functioning properly, road test the vehicle. Engine rpm should decrease when the "Scan" indicates the TCC driver has turned "ON."