Self-Diagnostic System: Notes

NOTE: For additional information and operating procedures for the self-diagnostic system, refer to TESTS W/CODES article in the ENGINE PERFORMANCE Section.

NOTE: The CHECK ENGINE light, located in the instrument cluster, is referred to as Malfunction Indicator Light (MIL) in this article.

The PCM monitors its inputs and outputs. When it detects a malfunction, it sets a code in the PCM and sends a signal to the Malfunction Indicator Light (MIL). The light (MIL) remains on until the malfunction is repaired. Trouble codes may be accessed at the Self-Test Output (STO) and Self-Test Input (STI) connectors, located near the battery.

If a sensor fails, the PCM will use a substitute value in its calculations to permit continued engine operation. In this condition, the vehicle will run, but driveability may be poor. Intermittent failures may result in the MIL flickering or going out after the fault goes away. The corresponding trouble code, however, will be stored in the PCM. If the fault does not recur, the related code will be erased from PCM memory.