Hard Failures

Hard failures cause CHECK ENGINE light to illuminate and remain on until the malfunction is repaired. If light comes on and remains on (light may flash) during vehicle operation, cause of malfunction must be determined by using DIAGNOSTIC FAULT CHARTS (if testing with voltmeter) or diagnostic CODE CHARTS (if testing with DRB-II). If a sensor fails, ECU will use a substitute value in its calculations to continue engine operation. In this condition, vehicle is functional, but loss of good driveability may result.