Chart C-8A Torque Converter Clutch (TCC) Electrical Diagnosis
Chart C-8A - Torque Converter Clutch (Part 1 of 2):
Wiring Diagram for Chart C-8A - Torque Converter Clutch:
CHART C-8A - TORQUE CONVERTER CLUTCH (TCC) 440 T4 (PART 1 OF 2)
Circuit Description:
The purpose of the 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 transaxle and the fuel economy of a manual transmission. The heart of the system is a solenoid located inside the automatic 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 transaxle. When the transaxle solenoid is deactivated, the torque converter clutch is released which allows the torque converter to operate in the conventional manner (fluidic coupling between engine and transaxle).
The TCC will engage on a warm engine under given road load in 3rd and 4th gears.
TCC will engage when:
^ Engine warmed up
^ Vehicle speed above a calibrated value (about 28 mph 45 km/h) and 3rd gear switch closed
^ Throttle position sensor output not changing, indicating a steady road speed
^ Transmission/transaxle fourth gear switch open
^ Brake switch closed.
Test Description: Numbers below refer to circled numbers on the diagnostic chart.
1. Light "OFF" confirms transmission third gear switch is open.
2. At about 25 mph, the transmission third gear switch should close. Test light will come "ON" and confirm battery supply and closed brake switch.
3. Grounding the diagnostic "test" terminal with engine "OFF" should energize the TCC solenoid.
This test checks the capability of the ECM to control the solenoid. If the light is "ON," check the items listed. If all OK but TCC applies at the wrong time, see CHART C-8A (2 of 2). Solenoids are turned "ON" or "OFF" by the ECM internal electronic switches called "drivers." Each driver is part of a group of four called quad-drivers. Failure of one can damage any other driver within the set. See CHART C-1.
Chart C-8A - Torque Converter Clutch (Part 2 of 2):
CHART C-8A - TORQUE CONVERTER CLUTCH (TCC) 440-T4 (PART 2 OF 2)
Test Description: Numbers below refer to circled numbers on the diagnostic chart.
4. Over 6 volts indicates an open CKT 446, transaxle connector, or a fourth gear switch stuck open.
5. With drive wheels at 50-55 mph, a voltage under 6 volts indicates CKT 446 is shorted to ground or faulty fourth gear switch if transaxle is actually in fourth gear.
6. Checks to determine if problem with CKT 446 is an internal transaxle problem.