Part 1 of 2

Chart C-8A Part 1 Of 2:

Wiring Diagram:

CIRCUIT DESCRIPTION:

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. The heart of the system is a solenoid located inside the transaxle which is controlled by the ECM.

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

The ECM turns "ON" the TCC when coolant temperature is above 65~C (149~F), TPS not changing, and vehicle speed above a specified value. For TCC lock-up speed and function of the gear switches, refer to circuit description on CHART C-8A PART 2 OF 2.


TEST DESCRIPTION:

1. Confirms 12 volt supply as well as continuity of TCC circuit.


2. Grounding the diagnostic terminal with the engine "OFF" should energize the capability of the ECM to control the TCC solenoid.

3. TCC solenoid coil resistance must measure more than 20 ohms. Less resistance will cause early failure of the ECM driver. Using an ohmmeter, 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.


DIAGNOSTIC AIDS:

The "Scan" tool only indicates when the ECM 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." To determine if the gear switches are functioning properly, perform the checks in CHARTS C-8A PART 2 OF 2. The switches will not prevent the TCC from functioning, but will affect TCC lock and unlock points. If the 4th gear switch circuit is always open, the TCC may engage as soon as sufficient oil pressure is reached.