P2A05
O2 Sensor Circuit Range/Performance Bank 2 Sensor 3
The third oxygen sensor on bank 2 (after a second catalyst stage on some vehicles) returns implausible values. Often related to sensor aging or mechanical exhaust leak upstream.
- 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
- Exhaust leak upstreamPossible
- Sensor element aged beyond calibration windowLess likely
Parts involved
- Oxygen Sensor
- Exhaust Pipe
P2A05 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.