Self Diagnosis Function

Fig. 4 Determining diagnostic codes:

The EFI system has a self diagnosis function to identify signals from the sensors with which the ECM controls the EFI system. If any trouble related to these sensors occurs, the difficulty in pinpointing the location of the malfunctioning component or area is greatly reduced. The areas being diagnosed are the oxygen sensor, coolant temperature sensor, turbocharger, air flow meter, ignition signal and the CPU (Central Processing Unit) of the ECM.
When a malfunction exists in the input signal to the ECM the instrument panel ``Check Engine'' lamp lights. This lamp remains lit until the malfunction is found and corrected. During this time, the malfunction is encoded in a two digit diagnostic code and stored in the ECM memory. To access this code, turn the diagnostic switch, located on the underside of the instrument panel to the right of the steering column, to the ``On'' position and note that the check engine lamp will begin flashing. Refer to Fig. 4, analyzing flashing codes.