"1990 Light Duty Truck R/V, P Models Electrical Diagrams and Diagnosis manual" Written for GMC dealership mechanics, this factory-published original wiring diagram shows you how to follow the wiring from bumper-to-bumper. It will help you understand connector configurations, and locate and identify circuits, relays, and grounds. You will not find these wiring diagrams in the factory shop manual. Wiring diagrams are black and white, but they frequently have color codes printed on each line of the diagram that represents a wire. It is a set of loose-leaf sheets. This manual covers 1990 GMC trucks, including Suburban, full-size Jimmy, half ton, three-quarter ton, one ton, R & V series pickup, stakebed, platform, and crew cab. This manual covers the "old style" R/V pickups for 1990, they have wing windows. If your pickup does not have wing windows, see the C/K series pickup diagram. Includes 2 wheel drive, 4 wheel drive, and dually models. Covers both gasoline and diesel engines. This book has 197 pages, measures 17.25" x 11" and is 0.63" thick. Buy now for the best electrical information available.