Hard Failures
WARNING: This page is about a different car, the 1992 Geo Prizm. However, it is still accessible from the selected car via links, so may be relevant.
Hard failures will cause CHECK ENGINE light to glow and remain on until malfunction is repaired. If light comes on and remains on (light may flash) during vehicle operation, cause of malfunction must be determined using diagnostic (code) charts. If a sensor fails, control unit will use a substitute value in its calculations to continue engine operation. In this condition, vehicle is functional, but loss of good driveability will most likely occur.