O2 Sensor Circuit No Activity / Slow Response (Bank 2 Sensor 1)
The ECU detects no switching activity or too slow a response from the upstream O2 sensor on bank 2. Typically aged or poisoned sensor, weak heater, or upstream exhaust leak.
Affected components
- Oxygen sensor b2s1
- Oxygen sensor heater circuit
- Exhaust manifold bank2
Common causes
- High likelihood: Sensor aged or poisoned
- Medium likelihood: Heater circuit weak
- Medium likelihood: Exhaust leak before sensor
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.