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.
Affected components
- Oxygen sensor downstream
- Oxygen sensor wiring
Common causes
- High likelihood: Downstream sensor aged
- Medium likelihood: Wiring chafed against exhaust
Possible symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
- A drive cycle may be required after repair
Related codes
Sources
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.