What it means
The post-cat oxygen sensors of bank 1 and bank 2 appear to be wired the wrong way around — bank 1 reacts when bank 2 should and vice versa. Typically after recent service.
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 and Bank 2 Sensor 2 are the oxygen sensors located after the catalytic converters on the two cylinder banks. The control module compares their signals to check that each sensor is reporting for the correct bank. It sets P0041 when the downstream signals appear to be assigned to opposite banks, often after sensor or wiring work.
Common causes
Most likely first.
- Bank 1 and bank 2 downstream oxygen-sensor connectors crossed
- Wiring repairs connected the sensors to the wrong circuits
- Incorrectly routed or installed sensor harness
Symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
How to diagnose it
- Check the freeze-frame data and compare live readings from Bank 1 Sensor 2 and Bank 2 Sensor 2 to see whether their responses appear to be attributed to the opposite banks.
- Inspect both downstream sensor connectors and harness routes, especially if the exhaust or sensors were recently serviced.
- Trace each connector to its sensor and confirm Bank 1 Sensor 2 is connected to the Bank 1 circuit and Bank 2 Sensor 2 to the Bank 2 circuit.
- Look for crossed or misrouted wiring from previous repairs, damaged insulation, corrosion, or loose connector pins.
- If the connections are correct, test each downstream sensor circuit for continuity and correct circuit assignment using the wiring diagram and manufacturer's procedures.
Common fixes
- Reconnect the Bank 1 Sensor 2 and Bank 2 Sensor 2 plugs to their matching harness connectors.
- Repair wiring that was crossed or connected to the wrong sensor circuits.
- Correct a misrouted harness and secure it away from heat or moving parts.
- Repair damaged connectors or wiring, then clear the code and confirm the two sensor signals are correctly assigned.
Can I keep driving?
If the engine runs normally, a short trip to diagnose the crossed downstream sensor connections is usually reasonable. Avoid prolonged driving because incorrect oxygen-sensor signals can affect emissions monitoring and may worsen fuel economy.
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.