Hard Failures

To prevent a false Diagnostic Trouble Code (DTC) from being stored in PCM memory, some malfunctions must be detected during 2 consecutive drive cycles. This applies to heated oxygen sensors (HO2S), fuel metering-related components, idle control system, Engine Coolant Temperature (ECT) sensor, Exhaust Gas Recirculation (EGR) system, Three-Way Catalytic (TWC) converter system, evaporative (EVAP) control system and other self-diagnostic functions. First occurrence of a detected malfunction is stored in PCM memory. If same malfunction is detected again after ignition switch is turned off and then back on, a hard failure DTC is stored and Malfunction Indicator Light (MIL) is turned on. MIL will remain on until detected malfunction is repaired. Malfunction can be determined by retrieving DTCs. See DIAGNOSTIC TROUBLE CODE IDENTIFICATION  and RETRIEVING DIAGNOSTIC TROUBLE CODES  .