Circuit/System Description
The fuel injector balance test is performed when a misfire, knock, excessive smoke, or rough running condition exists with no electrical DTCs. This test uses the Fuel Injector Balance and Compression Tests to identify cylinders that are not producing the designed power output. During the Fuel Injector Balance portion of the test, the ECM turns OFF individual injectors while the engine is running. The ECM adjusts for the drop in engine RPM during cancellation and may not change on the scan tool display. The lack of power at the cancelled cylinder will feel like a misfiring cylinder or vibration. If a fuel injector is turned OFF and there is a no difference felt when compared to the other cylinders, that cylinder is identified with the concern. The Compression Test will identify a mechanical issue with a cylinder.