Part 1OF 2

Chart C-8A Part 1 Of 2:

Chart C-8 Or C-8A Wiring Diagram:

CIRCUIT DESCRIPTION:

The purpose of the automatic transmission torque converter clutch 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. The heart of the system is a solenoid located inside the automatic transmission 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 transmission. When the transmission 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 transmission). The TCC will engage on a warm engine under given road load in 3rd gear.

The TCC will engage when:

^ Engine warmed up.
^ Coolant temperature is above 65~C (149~F).
^ Vehicle speed above a calibrated value (about 28 mph 45 km/h).
^ Throttle position sensor output not changing, indicating a steady road speed.
^ Brake switch closed.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. This test checks the continuity of the TCC circuit from the fuse to the ALDL connector.

2. When the brake pedal is released, the light should come back "ON" and then go "OFF" when the diagnostic terminal is grounded. This tests CKT 422 and the TCC driver in the ECM.

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."