What it means
The downstream oxygen sensor signal is fixed at a high voltage, indicating either a continuously rich downstream reading (less common, since post-cat exhaust should be more stable) or a short to supply voltage in the signal circuit.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Bank 1 Sensor 2 measures oxygen in the exhaust after the catalytic converter. This code sets when the control module sees its signal stay above the expected range, which may reflect a rich exhaust reading or a signal wire shorted to a voltage source.
Common causes
Most likely first.
- Signal wire shorted to supply voltage
- Downstream sensor failed
- Connector pins corroded - high contact resistance
Symptoms
- Check engine light on
- Failed emissions test
How to diagnose it
- Save freeze-frame data and check the engine conditions present when the high signal was recorded.
- Inspect the Bank 1 Sensor 2 harness and connector for melted insulation, shorts to a powered wire, corrosion, or loose terminals.
- Check for exhaust leaks and review fuel-control data that could help distinguish a genuine rich condition from an electrical fault.
- Watch Bank 1 Sensor 2 live data with the engine warm and compare it with the upstream sensor and other available mixture data.
- Test the downstream signal circuit for a short to voltage and verify the sensor and connector against the wiring diagram and manufacturer's specification.
Common fixes
- Repair wiring that is shorted to a supply wire or damaged by exhaust heat.
- Clean or repair corroded, loose, or damaged connector pins.
- Correct an engine condition causing persistently rich exhaust if data supports that diagnosis.
- Replace Bank 1 Sensor 2 if its circuit is sound and the sensor continues to report an implausibly high signal.
Can I keep driving?
If the engine runs normally, you can generally drive a short distance for diagnosis, but the vehicle may fail an emissions test. If it runs rough, smells strongly of fuel, or the check-engine light flashes, stop driving to reduce the risk of damage.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.