Hard Code Failures
WARNING: This page is about a different car, the 1995 Jeep Wrangler, 1995 Jeep Grand Cherokee, and 1995 Jeep Cherokee. However, it is still accessible from the selected car via links, so may be relevant.
During each ignition on/off cycle, if a DTC is seen every time PCM checks a specific circuit or function, a hard code DTC is stored in PCM memory. Hard code failures cause MIL to glow 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 using self-diagnostic tests. If a sensor fails, PCM will use a substitute value to operate failed system, allowing engine to operate in limp-in mode. In this condition, vehicle will run, but driveability may be poor.