System Diagnosis: Notes

WARNING: This page is about a different car, the 1994 Mitsubishi Diamante. However, it is still accessible from the selected car via links, so may be relevant.

System diagnosis can be accomplished using an appropriate scan tester, a voltmeter or the Malfunction Indicator Light (MIL). See RETRIEVING CODES . Engine Control Module (ECM) monitors several different engine control system circuits. If an abnormal input signal occurs, a trouble code is stored in ECM memory and assigned a trouble code number. Each circuit has its own trouble code number and message. A specific trouble code indicates a particular system failure, but does not indicate that cause of failure is necessarily within system.

A trouble code does not condemn any specific component; it simply points out a probable malfunctioning area. If a trouble code is set, ECM will turn on MIL. System malfunctions encountered are identified as either hard failures or intermittent failures as determined by ECM.