With Automatic Transmission

FUEL INJECTOR BALANCE TEST WITH TECH 2 (WITH AUTOMATIC TRANSMISSION)

CIRCUIT DESCRIPTION
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.

TEST DESCRIPTION

Steps 1-4:

Steps 5-7:

Steps 8-10:

The numbers below refer to the step numbers on the diagnostic table.
4. The balance rate adjustments are utilized by the ECM only at idle. The balance rates are the fuel adjustments for each individual cylinder based on the variations in engine crankshaft speed. A positive value indicates that fuel is being added to each cylinder event, such as with poor engine compression or a fuel injector that is not flowing enough fuel. A negative value indicates fuel being removed from each cylinder event, such as a fuel injector that is flowing too much fuel. The balance rates will change depending on if the transmission is in Neutral or Drive.
5. This step determines if the ECM can control a stable fuel pressure. A high balance rate may be caused by a fuel injector or compression only if the ECM can control fuel pressure.
6. The Cylinder Power Balance Test may be performed at any engine speed or load from idle to wide-open throttle (WOT). There is a 5 minute time limit for each test. The ECM and scan tool must both be powered down to reset the timer.