O2 Sensor Circuit No Activity / Slow Response (Bank 1 Sensor 2)
The ECU detects no switching or excessively slow response from the downstream oxygen sensor on bank 1. Typical for an aged or poisoned sensor; downstream sensors should show a relatively flat signal but must respond to fueling changes during diagnostic monitor runs.
Affected components
- Oxygen sensor b1s2
- Oxygen sensor heater circuit
- Catalytic converter bank1
Common causes
- High likelihood: Sensor aged or poisoned
- Medium likelihood: Sensor heater circuit weak
- Low likelihood: Catalytic converter so degraded that downstream signal mirrors upstream
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.