Section 128 (Engine Controls - Basic Diagnostic Procedures - 6.5L Diesel)
WARNING: This page is about a different car, the 1998 GMC Pickup, 1998 GMC Cab & Chassis, 1998 Chevrolet Pickup, and 1998 Chevrolet Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.