Chart C-8A Torque Converter Clutch (TCC) Functional Check

Chart C-8A:

Torque Converter Schematic:

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. The heart of the system is the TCC apply solenoid located inside the transaxle which is controlled by the Powertrain Control Module (PCM).

When the solenoid coil is activated ("ON"), the Torque Converter Clutch is applied which results in a straight through mechanical coupling from the engine to the wheels. When the solenoid coil is deactivated ("OFF"), the Torque Converter Clutch is released which allows the torque converter to operate in the conventional manner (fluid coupling between engine and transaxle).

The TCC Pulse Width Modulated (PWM) solenoid varies the hydraulic pressure at the converter clutch regulator valve to make locking and unlocking of TCC smoother. TCC will engage when:

^ Engine warmed up.
^ Vehicle speed above a calibrated value (about 28 mph 45 kp/h).
^ Throttle position sensor output not changing, indicating a steady road speed.
^ Brake switch closed.
^ Vehicle is in 3rd or 4th gear.
^ Vehicle is operating "hot mode," which will cause the TCC to be engaged in 2nd gear.
^ "Hot mode" will be in effect when transaxle temperature exceeds 130°C (266°F).

CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.


NOTICE:
When connecting a test light or DVM to the connectors, use connector test adapter kit J 35616 or extension harness J 38835 to avoid damaging the connector terminals.


1. Determines whether fault is caused by a faulty solenoid or control circuit.
2. Checks availability of B+ on CKT 241.
3. Check. the PCM's capability to pulse the PWM solenoid "ON" and "OFF."

DIAGNOSTIC AIDS
The Tech 1 only indicates when the PCM has commanded the TCC solenoid driver "ON" and 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 Tech 1 indicates the TCC driver has turned "ON."

The TCC may engage in 2nd gear if the vehicle is operating in "Hot Mode." "Hot Mode" operation will be in effect when transaxle temperature exceeds 130°C (266°F).