P2A01
O2 Sensor Circuit Range/Performance Bank 1 Sensor 2
The rear oxygen sensor on bank 1 does not show the expected slow steady-state behaviour after the catalyst. Either the sensor is degraded or the catalyst itself behaves abnormally.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
Common causes
Ordered by how often each turns out to be the cause.
- Sensor agingCommon
- Catalyst agingPossible
- Sensor element aged beyond calibration windowLess likely
Parts involved
- Oxygen Sensor
- Catalytic Converter
P2A01 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.