System Diagnosis: Notes

WARNING: This page is about a different car, the 1992 Mitsubishi Precis, 1992 Mitsubishi Galant, and 1992 Mitsubishi Diamante. However, it is still accessible from the selected car via links, so may be relevant.

System diagnosis can only be accomplished using a voltmeter or appropriate scan tester. See ENTERING ON-BOARD DIAGNOSTICS. Engine 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 indicates a particular system failure, but it does not indicate that cause of failure is necessarily within system.

A fault code does not condemn any specific component; it simply points out a probable malfunctioning area. If a fault code is set, ECU will turn on CHECK ENGINE light. Fault codes can be confirmed by using a voltmeter. System malfunctions encountered are identified as either hard failures or intermittent failures as determined by ECU.