P0136
O2 Sensor Circuit Malfunction (Bank 1, Sensor 2)
A general fault has been detected in the downstream (post-catalyst) oxygen sensor on bank 1. The downstream sensor monitors catalyst efficiency rather than fuel mixture; with no signal, the catalyst monitor cannot run.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: easy
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.
- Downstream sensor agedCommon
- Wiring chafed against exhaustPossible
Parts involved
- Oxygen Sensor Downstream
- Oxygen Sensor Wiring
P0136 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.