P0156: Downstream O2 sensor circuit malfunction (Bank 2 Sensor 2)
You can keep driving. Get it checked when convenient.
Can I drive with P0156?
Yes, you can keep driving. Downstream monitoring sensor issue on Bank 2; little immediate effect on engine safety or driving.
What does P0156 mean?
P0156 stands for O2 Sensor Circuit Malfunction (Bank 2, Sensor 2).
Symptoms you may notice
- Check engine light on with no noticeable change in how the car drives
- Vehicle fails state emissions smog test
- Normal engine power and shifting
How much does it cost to fix?
Repair costs for code P0156 depend on the specific underlying root cause, ranging from simple DIY checks to component replacement. The table below lists the most common causes and rough price ranges in USD:
- Faulty downstream oxygen sensor
- Damaged undercarriage wiring harness
- Corroded electrical plug
- Exhaust leak after catalytic converter
What to do next
- Inspect the wiring to Bank 2 rear sensor beneath the vehicle.
- Check connector for road grime and moisture.
- Replace Bank 2 Sensor 2 oxygen sensor.
Last updated: October 2026
Related codes
General guidance only, not a professional diagnosis. If the check-engine light is flashing, or the car is running rough, overheating or losing power, stop driving and get help.
About this code
Code P0156 is the Bank 2 rear oxygen sensor monitor. It solely monitors catalyst efficiency. usually safe to drive for a short time, but get it checked to drive.