Circuit Description
WARNING: This page is about a different car, the 2006 GMC Yukon XL, 2006 Chevrolet Suburban, and 2006 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
The scan tool first energizes the fuel pump and then the injectors for a precise amount of time allowing a measured amount of fuel into the manifold. This causes a drop in system fuel pressure that can be recorded and used to compare each injector.