Self-Diagnostic System
WARNING: This page does not describe the selected car, but rather 22 other vehicles, including the 1990 GMC Vandura Special, 1990 GMC Vandura, 1990 GMC Value Van, 1990 GMC Suburban, and 1990 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.