What it means
O2 Sensor Out of Range During Deceleration Bank 1 Sensor 2: the control module has detected this fault condition. (Code P239E)
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 downstream oxygen sensor in the exhaust stream for the cylinder bank that contains cylinder 1. During deceleration, the control module checks whether this sensor's reading stays within the expected range; this code sets when the bank 1 downstream reading falls outside that range.
Common causes
Most likely first.
- Bank 1 sensor 2 oxygen sensor aging or responding slowly
- Exhaust leak near the sensor
- Sensor 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 data and live bank 1 sensor 2 readings during deceleration to see when the out-of-range condition occurs.
- Inspect the exhaust joints near bank 1 sensor 2 for leaks that could draw in air and affect its sample.
- Check the sensor body, connector, and wiring along the bank 1 exhaust for damage, contamination, or poor connections.
- Compare bank 1 sensor 2 behavior with the upstream sensor and with the other bank's downstream sensor, if equipped, to look for an implausible response.
- Test the sensor circuit and heater as applicable, then compare sensor operation with the manufacturer's specification before replacing parts.
Common fixes
- Repair an exhaust leak near bank 1 sensor 2.
- Restore damaged wiring or clean and secure a poor sensor connector.
- Replace a contaminated or slow bank 1 sensor 2 if circuit and exhaust checks pass.
- Repair the sensor circuit fault identified by testing.
Can I keep driving?
If the vehicle drives normally, you can generally make a short trip for diagnosis, but arrange repair soon because emissions performance may be affected and the vehicle may fail an emissions test. Stop if rough running or hesitation becomes severe.
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.