Download Tests/Procedures: Potential Causes: 1. Perform a fuel injector balance test for all cylinders. If a fuel injector concern exists, it is possible to misfuel an entire bank of the engine, causing multiple cylinders on the same bank to misfire even though the root cause is a single fuel injector. The engine computer recognizes all the extra oxygen and adds fuel to the engine bank. This is verifiable by higher injector pulse on the affected bank. 2. Use the scan tool to turn off the fuel enable. This is found using the special functions/output controls of the scan tool. This will maintain fuel trim numbers at 0%. Check for the entire bank to stop misfiring and concentrate on a single cylinder misfire. The single cylinder misfire can be the cause of the O2 sensor showing lean exhaust. 3. Check for excessive exhaust backpressure. This can affect only one bank if equipped with 2 catalytic converters. This is often verifiable by reduced injector pulse on the affected bank. 4. Swap the position 1 O2 sensors side to side to see if the misfires move to the other bank of the engine. If so, replace the O2 sensor.