What it means
The control module detects that the Bank 1 Sensor 2 oxygen-sensor signal remains lean or is biased lean. This code does not by itself diagnose a failed sensor or catalytic converter.
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 is the oxygen sensor downstream of the catalytic converter on the bank 1 exhaust. The control module sets this code when its signal stays lean or appears lean for too long, which can result from the sensor, an exhaust leak near it, or its signal circuit.
Common causes
Most likely first.
- Faulty downstream oxygen sensor
- Exhaust leak near the sensor
- Signal wiring or connector fault
Symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
How to diagnose it
- Check freeze-frame and live data for bank 1 Sensor 2, noting whether its signal remains lean as engine conditions change and whether related fuel-trim or misfire codes are present.
- Inspect the exhaust around bank 1 Sensor 2 and the catalytic converter outlet for leaks that could draw oxygen into the sensor reading.
- Inspect the sensor's connector and signal wiring for heat damage, corrosion, loose pins, or contact with the exhaust.
- Compare bank 1 Sensor 2 activity with the upstream sensor and check the sensor heater and signal circuit using the manufacturer's procedure.
- If no leak or circuit fault is found, test the sensor response under the manufacturer's conditions before replacing it.
Common fixes
- Repair an exhaust leak near bank 1 Sensor 2.
- Repair damaged or corroded wiring and connector terminals in the sensor circuit.
- Replace bank 1 Sensor 2 if it fails response or circuit testing.
- Address any upstream engine fault shown by related codes that could keep the exhaust mixture lean.
Can I keep driving?
You can usually drive gently if the engine runs smoothly, but arrange diagnosis soon because fuel use or emissions may worsen. Stop if it begins running very rough or loses power.
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.