Following is a listing of vacuum diagrams for most of the engine and emissions package combinations covered by this guide. Because vacuum circuits will vary based on various engine and vehicle options, always refer first to the vehicle emission control information label, if present. Should the label be missing, or should vehicle be equipped with a different engine from the truck's original equipment, refer to the diagrams below for the same or similar configuration.
If you wish to obtain a replacement emissions label, most manufacturers make the labels available for purchase. The labels can usually be ordered from a local dealer. Speak to the dealership's parts department first to make sure you copy down all the identification codes they will need to order the replacement label.