Self-Diagnostic System: Notes
WARNING: This page does not describe the selected car, but rather 22 other vehicles, including the 1991 GMC Vandura Special, 1991 GMC Vandura, 1991 GMC Value Van, 1991 GMC Suburban, and 1991 GMC Rally Camper Special. However, it is still accessible from the selected car via links, so may be relevant.
The 6.2L light duty emissions system includes a self-diagnostic system which can determine input signal circuit malfunctions. Input signal circuits determine engine function control.