Hard Failures

Hard failures cause SERVICE ENGINE SOON/MIL to illuminate and remain on until problem is repaired. If SERVICE ENGINE SOON/MIL comes on and remains on (light may flash) during vehicle operation, cause of malfunction must be determined using diagnostic (code) tests. If a sensor fails, PCM will use a substitute value in its calculations to continue engine operation. In this condition, commonly known as limp-in mode, vehicle runs but driveability will not be optimum.