Torque Converter Clutch (TCC)

Circuit Description:
The purpose of the automatic [1][2]Torque Converter Clutch (TCC) feature is to eliminate the power loss of the torque converter stage when the vehicle is in a cruise condition. This allows the convenience of the automatic transmission and the fuel economy of a manual transmission.
Fused battery voltage is supplied to the TCC solenoid through the TCC brake switch.
The ECM will engage TCC by grounding CKT 422 to energize the solenoid.
The ECM completes the circuit whenever the TPS exceeds a calibrated valve for throttle opening.

Test Description:
Numbers below refer to the circled number on the diagnostic chart,
1. Checks for complete circuit, from key switch through solenoid, up to test point. Test light should be "ON" normally, since ECM has not completed circuit yet.
2. Checks continuity through brake switch and TCC solenoid.
3. Checks for ECM to complete circuit to ground to energize TCC solenoid and engage TCC. Test light should normally go out when ECM completes circuit.
4. Checks for TPS signal. If signal to ECM is correct, fault is in ECM connection or ECM. If TPS signal to ECM is incorrect (voltage), proper operation will not occur.
5. Checks for ground in circuit to ECM terminal "C5." Normally, light should be "OFF."
6. Checks for voltage to terminal "A" of TCC connector. Light should normally be "ON."
7. Checks for complete circuit from voltage to ground, via TCC test terminal in ALDL. Normally, light should go "ON," if harness is good.

Diagnostic Aids:
Solenoid coil resistance must measure more than 20 ohms. Less resistance will cause early failure of the ECM "DRIVER." Using an ohm meter, check the solenoid coil resistance of all ECM controlled solenoids and relays, before installing a replacement ECM. Replace any solenoid, or relay, that measures less than 20 ohms resistance.