Circuit Description

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The Fuel Injector Balance Test is performed when a misfire, knock, excessive smoke, or rough running condition exists with no electrical diagnostic trouble codes (DTCs). During the Cylinder Power Balance portion of the test, the engine control module (ECM) turns OFF individual injectors while the engine is running and the scan tool displays engine RPM. The ECM adjusts for the drop in engine speed, so the power contribution of each cylinder must be felt by the technician. If a fuel injector is turned OFF and there is a different power contribution observed when compared to the other cylinders, that cylinder is identified with the complaint. If the customer complaint occurs during idle or during off-idle tip in acceleration, the balance rates are used to identify the cylinder with a fault related to the fuel injector or engine compression. If a fuel injector is turned OFF and the engine noise or smoke disappears, that cylinder has a fuel injector or engine compression condition.