System Diagnosis

The AMC TBI fuel injection system is equipped with a self-diagnostic capacity. When a failure occurs within the system, a trouble code is stored in the ECU.

To recall trouble codes, install a test light between pins 2 and 4 of diagnostic connector D2. Push the WOT switch lever on the throttle body to wide open position and close the ISC motor plunger (activates closed throttle switch). Turn the ignition switch on and observe the test bulb.

The ECU test bulb will light for a moment, then go out. This should always occur, regardless of whether or not any trouble codes are stored, to indicate that the ECU is functional.

The bulb will then indicate all stored trouble codes as a series of brief flashes (flash, flash for code 2, flash, flash, flash, for code 3, etc.). If multiple trouble codes are stored in the ECU, the first code stored is indicated first, followed by a short pause, and any remaining codes. After a longer pause, the cycle repeats. Each trouble code indicates the malfunction of a specific sensor or sensors. Note codes.

Some injection system difficulties or abnormalities may occur without setting a trouble code. If this happens, refer to specific problem descriptions listed after trouble code references.