Chart C-8A Torque Converter Clutch (TCC) Diagnosis

Chart C-8A - Torque Converter Clutch (Electrical Diagnosis):

TCC Solenoid Wiring Circuit:

CIRCUIT DESCRIPTION:
The purpose of the Torque Converter Clutch (TCC) 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 transaxle and the fuel economy of a manual transaxle.

Voltage is supplied to the TCC solenoid through the brake switch and transaxle third gear apply switch. The ECM will engage TCC by grounding CKT 422 to energize the solenoid.

TCC will engage under the following conditions:
^ Vehicle speed exceeds about 25 mph (40 km/h).
^ Engine coolant temperature exceeds 65°C (145°F).
^ Throttle Position (TP) sensor is not changing faster than a calibrated rate (steady throttle).
^ Brake switch closed.
^ Transaxle 3rd gear switch is closed.

TEST DESCRIPTION: Number(s) below refer to circled number(s) on the diagnostic chart.
1. This test should be performed with the aid of a helper, to operate the scan tool and observe the RPM fluctuation.
2. Entering the "Field Service Mode" forces the ECM to close the TCC control driver circuit completing the path for current which should light the test light.
3. Perform this test with the aid of a helper. The 3rd gear switch must be engaged while measuring the TCC solenoid resistance.

DIAGNOSTIC AIDS:
Fused battery ignition is supplied to the TCC solenoid through the brake switch. The ECM will engage TCC by grounding CKT 422 to energize the solenoid. An engine coolant thermostat that is stuck open or opens at too low a temperature may result in an inoperative TCC.