2020 Subaru Forester P code Page 31

Front oxygen (A/F) sensor cover has some ventilation holes for exhaust gas. Clogged ventilation holes are diagnosed.

When the holes are clogged, the A/F output variation becomes slow comparing with the actual A/F variation because oxygen which reaches

the zirconia layer is insufficient. Therefore, if the sensor cover holes are clogged, the rich to lean judgment in the ECM is delayed when the

actual change from rich to lean occurs. Judge as NG when the actual movement in comparison to the ECM control amount is slow.

2. COMPONENT DESCRIPTION