System Diagnosis: Notes

The self-diagnostic capabilities of this system, if properly used, can simplify testing. PCM monitors several different engine control system circuits.

If a problem is sensed with a monitored circuit, a fault code is stored in PCM, CHECK ENGINE light illuminates and PCM enters limp-in mode. In limp-in mode, PCM compensates for component failure by substituting information from other sources. This allows vehicle operation until repairs can be made.

Once fault codes are known, to determine the questionable circuit refer to CHARGING SYSTEM FAULT CODES  table under ENTERING ON-BOARD DIAGNOSTICS.

Perform circuit tests to repair or replace components as required. If problem is repaired or ceases to exist, the PCM will cancel that fault code after 50 ignition on/off cycles. To clear codes, refer to appropriate ERASING FAULT CODES heading under ENTERING ON-BOARD DIAGNOSTICS.

A specific fault code results from a particular system failure. Components in that system are not necessarily the reason for that failure. The fault code does not condemn a specific component, it calls out a CIRCUIT malfunction.