Hard Failures

Hard failures cause MIL to illuminate and remain on until problem is repaired. If light comes on and remains on during vehicle operation, cause of malfunction must be determined by retrieving Diagnostic Trouble Codes (DTCs). See RETRIEVING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM. If a sensor fails, ECM will use a substitute value in its calculations to continue engine operation. In this condition, commonly know as limp-in mode, the vehicle runs but driveability may not be optimum.