DTC P219A: General Description
The powertrain control module (PCM) measures the air/fuel ratio by the signal from the rear air/fuel ratio (A/F) sensor (bank 1, sensor 1). If the air/fuel ratio varies between the cylinders, the signal from the rear A/F sensor (bank 1, sensor 1) fluctuates while all cylinders complete the combustion cycle (two engine revolutions as one cycle). The PCM varies the engine air/fuel ratio at a specified frequency to measure the dispersion between the cylinders, and obtained air/fuel ratio fluctuation are filtered to extract the value. If the ratio between the integrated filtered output and the integrated varied air fuel ratio is a set value or more, the PCM detects a malfunction and stores a DTC.