Self-Diagnostic System: Notes
WARNING: This page does not describe the selected car, but rather 10 other vehicles, including the 1994 GMC Yukon, 1994 GMC Suburban, 1994 GMC Pickup, 1994 GMC Cab & Chassis, and 1994 GMC C3500 HD. However, it is still accessible from the selected car via links, so may be relevant.
The PCM is equipped with a self-diagnostic system which detects system failures or abnormalities. When a malfunction occurs, PCM illuminates the SERVICE ENGINE/THROTTLE SOON light located on instrument panel. When malfunction is detected and light is turned on, a corresponding trouble code is stored in PCM memory. Malfunctions are designated as either "hard failures" or "intermittent failures". For procedures on retrieving stored codes, see appropriate TESTS W/CODES article in the ENGINE PERFORMANCE section below.