Monitor Description

Fuel System Air Fuel Ratio Cylinder Imbalance Monitor 

The ECM uses the air fuel ratio sensor and crankshaft position sensor to monitor the difference in air fuel ratios between the cylinders caused by differences in injection volumes between the cylinders, leakage in the intake or exhaust system, etc.

When the air fuel ratios of the cylinders are lean or rich with respect to each other, the ECM determines that there is a malfunction, illuminates the MIL and stores a DTC.

Air Fuel Ratio Sensor Monitoring Method: P219A is stored primarily when a rich side imbalance is detected. 

When the system detects a difference in air fuel ratios between the cylinders due to fluctuation in the air fuel ratio sensor output over 1 engine cycle (2 crankshaft revolutions), the ECM determines that there is a malfunction.

Crankshaft Position Sensor Monitoring Method: P219C, P219D, P219E, and/or P219F are stored primarily when a lean side imbalance is detected. 

The system monitors the engine speed variation and when the variation becomes large, the ECM determines that there is a difference in air fuel ratios between the cylinders, which it determines to be a malfunction.