What it means
The downstream oxygen sensor on bank 2 reports a constant rich signal during a forced-lean command. Suggests a failed downstream sensor or a sensor contaminated by oil/coolant from upstream engine wear.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Bank 2 Sensor 2 is the oxygen sensor after the first catalytic converter on bank 2. The control module checks its signal during a commanded lean condition; this code sets when the signal continues to indicate rich instead of responding as expected.
Common causes
Most likely first.
- Downstream oxygen sensor failed or aged
- Signal wire shorted to voltage
- Exhaust leak near the sensor
- Fuel mixture actually rich from an engine or fuel-system fault
Symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
How to diagnose it
- Read freeze-frame data and compare bank 2 Sensor 2 live data with the upstream bank 2 sensor during a commanded lean event to see whether the downstream signal changes.
- Check for exhaust leaks around the bank 2 Sensor 2 bung and nearby joints, since outside air can distort the reading.
- Inspect the sensor connector and harness for heat damage, corrosion, loose pins, or a signal wire shorted to voltage.
- Check whether fuel trims or other codes point to an actual rich-running condition before condemning the downstream sensor.
- Test the sensor signal and heater circuit using the vehicle wiring diagram and manufacturer's specifications, then replace the sensor if its response remains stuck.
Common fixes
- Repair an exhaust leak near bank 2 Sensor 2.
- Repair damaged wiring or a poor connector at the bank 2 Sensor 2 circuit.
- Correct the engine or fuel-system fault causing a genuinely rich mixture.
- Replace a contaminated or unresponsive bank 2 Sensor 2.
Can I keep driving?
If the engine runs smoothly and the warning light is steady, a short trip may be possible, but arrange diagnosis soon because fuel use and emissions can rise. Stop driving if the light flashes or the engine runs badly, since an underlying rich fault can damage the catalytic converter.
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.