Disconnect both O2 sensors (front and rear), start engine and let idle. Check MVB's 41/4 and 136/4 and verify have both changed from a 1 to a 0 (you may have to drive the car 4 miles to get them to reset to 0). Also a key cycle may be required for values to reset. This forces the ECM to re-learn the O2 sensor adaptation. Once MVB 41/4 and 136/4 read 0, re-connect the O2 sensors, road test and recheck for faults.
