System Diagnosis: Notes

NOTE: Chrysler Motors recommends using DRB-II to diagnose system. Voltmeter usage has limited diagnostic capabilities but can be used if DRB-II is not available.

The Electronic Control Unit (ECU) monitors several different engine control system circuits. If an abnormal input signal occurs, a fault code is stored in ECU memory and given a fault code number. Each circuit has its own fault number and message. A specific fault code results from a particular system failure. It is NOT necessarily the reason for that failure. The fault code does not condemn a specific component. The fault code calls out a probable malfunction area. If a critical fault code is set, the ECU will turn on CHECK ENGINE light. All fault codes except speed sensor are considered critical.

Fault codes can be confirmed by using a voltmeter, DRB-II, or appropriate scan tester. See ENTERING ON-BOARD DIAGNOSTICS (USING VOLTMETER) or ENTERING ON-BOARD DIAGNOSTICS (USING DRB-II) . By using DRB-II, the self-diagnostic capabilities of this system can simplify testing and reduce diagnostic time.

System malfunctions encountered are identified as either hard faults or intermittent faults as determined by the ECU.