Component Diagnostic Charts (C-Charts) - Port Fuel Injection

Chart C-8A:

Chart 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.

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

The TCC will engage when:


^ Vehicle speed above a calibrated value (about 30 mph 48 km/h).
^ Engine temperature is above 70~C (156~F).
^ Throttle position sensor output not changing, indicating a steady road speed.
^ Transaxle third gear switch is closed.
^ Brake switch closed.

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

1. Light "OFF" confirms that transaxle third gear apply switch is open.

2. At 48 km/h (30 mph), the transmission third gear switch should close. Test light will light and confirm battery supply, and close the brake switch.

3. Grounding the diagnostic terminal with the engine "OFF" should energize the TCC solenoid. This test checks the capability of the ECM to control the solenoid.

DIAGNOSTIC AIDS:

An engine coolant thermostat that is stuck open or opens at too low a temperature may result in an inoperative TCC.