Self-Diagnostic System: Notes

WARNING: This page does not describe the selected car, but rather 26 other vehicles, including the 1993 GMC Yukon, 1993 GMC Vandura Special, 1993 GMC Vandura, 1993 GMC Value Van, and 1993 GMC Suburban. However, it is still accessible from the selected car via links, so may be relevant.

Gasoline vehicles are equipped with a Powertrain Control Module (PCM). The PCM controls engine/emission functions, and electronic-controlled transmission functions. For additional information on self-diagnostic system for gasoline vehicles, see THEORY/OPERATION and appropriate TESTS W/CODES article in this sections.

Diesel vehicles with 4L80-E transmission are equipped with a Transmission Control Module (TCM). TCM controls only the electronic transmission. Unless specifically stated otherwise, references to PCM also apply to TCM-equipped vehicles.

Control module is equipped with a self-diagnostic system, which detects system failures or abnormalities. When a malfunction occurs, control module will illuminate the SERVICE ENGINE SOON light located on instrument panel. When malfunction is detected and light is turned on, a corresponding trouble code will be stored in control module memory. To retrieve stored codes, see ENTERING & EXITING DIAGNOSTIC MODE . Malfunctions are recorded as either hard failures or intermittent failures.