What it means
An open or fault is detected in the negative current control circuit for the Bank 1 Sensor 3 oxygen sensor. This can interfere with the sensor's air-fuel measurement.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Bank 1 Sensor 3 is the third oxygen sensor position along the exhaust on the engine's Bank 1 side; its negative-current control circuit is part of the sensor's measurement electronics. The control module sets P2A3B when it detects an open or electrical fault in this negative-current path, which can disrupt the sensor's air-fuel measurement.
Common causes
Most likely first.
- Open or damaged wiring
- Faulty oxygen sensor
- Poor connector contact
Symptoms
- Check-engine light
How to diagnose it
- Capture freeze-frame data and inspect Bank 1 Sensor 3 live data for missing or implausible readings when the fault occurred.
- Locate Bank 1 Sensor 3 and inspect its connector and exhaust-area harness for heat damage, chafing, corrosion, or a loose or backed-out pin.
- Check continuity and connector contact in the negative-current control wire using the manufacturer's wiring diagram and procedure.
- Test the circuit for unintended shorts to ground or power and compare sensor electrical checks with the manufacturer's specification.
- If wiring and connections pass, test Bank 1 Sensor 3 and the module circuit before deciding which component failed.
Common fixes
- Reseat the Bank 1 Sensor 3 connector and repair loose terminals.
- Repair an open or damaged negative-current control wire.
- Replace Bank 1 Sensor 3 if its negative-current circuit fails the specified test.
- Repair a confirmed control-module connector or circuit fault.
Can I keep driving?
This fault can make Bank 1 Sensor 3 measurements unreliable and affect emissions, although drivability may remain normal. Limit unnecessary driving and arrange diagnosis soon; stop if the engine runs poorly or the warning light flashes.
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.