What it means
The PCM detects that the O2 sensor signals from bank 1 sensor 3 and bank 2 sensor 3 are swapped — typically a wiring crossover after sensor replacement.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
This code concerns the paired third-position oxygen sensors on bank 1 and bank 2, where the exhaust system has a Sensor 3 on each bank. The control module sees the two signals behaving as though their inputs are crossed, often after the sensor connectors or harnesses were swapped during service.
Common causes
Most likely first.
- Bank 1 and bank 2 sensor 3 connectors crossed
- Oxygen-sensor wiring routed to the wrong bank
- Incorrect sensor installation after service
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 3 and bank 2 Sensor 3 to confirm the signals appear assigned to the opposite banks.
- Inspect both sensor connectors and follow each harness to verify that the bank 1 Sensor 3 lead reaches the bank 1 sensor and the bank 2 lead reaches bank 2.
- Look for recent sensor or exhaust service and check whether connectors were crossed or sensors installed in the wrong positions.
- Verify connector pin condition and circuit continuity for both sensor signal and heater circuits using the wiring diagram.
- After correcting the routing or connections, clear the code and confirm both sensor readings respond independently in live data.
Common fixes
- Reconnect the bank 1 and bank 2 Sensor 3 plugs to their correct sensors.
- Reroute harness branches so each third-position sensor lead reaches the correct bank.
- Correct sensor placement if the two sensors were installed in the wrong bank positions.
- Repair connector or wiring damage found during the signal and heater circuit checks.
Can I keep driving?
If the light is steady and the vehicle runs normally, a short trip is generally reasonable, but the crossed readings can impair emissions monitoring. Avoid extended driving until the connections are corrected, especially if fuel economy or drivability worsens.
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.