System Diagnosis: Notes

NOTE: Chrysler Corp. recommends using DRB to diagnose system. Voltmeter usage has limited diagnostic capabilities, but can be used if DRB 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 Malfunction Indicator Light (MIL). All fault codes except speed sensor are considered critical.

Fault codes can be confirmed by using a voltmeter, DRB or appropriate scan tester. See ENTERING ON-BOARD DIAGNOSTICS (USING VOLTMETER) or ENTERING ON-BOARD DIAGNOSTICS (USING DRB). By using DRB, 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.