System Diagnosis

The self-diagnostic capabilities of this system, if properly utilized, can greatly simplify testing. If, at any time, the logic module receives an incorrect signal or no signal from either the Coolant Temperature Sensor, MAP sensor or TPS, a Power Loss Lamp on the instrument panel is illuminated. This lamp acts as a warning device to inform the operator that a malfunction in the system has occurred and immediate service is required.

When certain malfunctions occur, the logic module enters the "Limp In Mode". In this mode, the logic module attempts to compensate for the failure of the particular component by substituting information from other sources. Ideally, this will allow the vehicle to be operated until proper repairs can be made.

If the Power Loss Lamp comes on, or if certain driveability or engine performance difficulties exist, the probable source of these difficulties may be determined by entering "On Board Diagnosis" and recording the fault codes as they are displayed.

Once these codes are known, refer to the fault codes listing to determine the questionable circuit. Then use the wiring diagram and connector identification charts to locate testing points for each circuit. With the ignition on, the wire(s) in question should read as specified under Wire Function in tables. Test circuits and repair or replace as needed. If the problem is repaired or ceases to exist, the logic module cancels the fault code after 30 ignition on/off cycles.