Hard Faults

A "Hard Fault" will cause the "SERVICE ENGINE SOON" (SES) light to illuminate and remain on until the malfunction is repaired. If light comes on and remains on (or flashes) during vehicle operation, cause of malfunction must be determined using diagnostic code charts. If a sensor fails, ECM will use a substitute value in its calculations to continue engine operation. In this condition, vehicle is functional, but driveability may be affected.