What it means
The bank 1 sensor 2 oxygen sensor negative current control circuit is below the expected range. The code does not by itself establish a short to ground or predict mixture effects.
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 on the bank containing cylinder 1. The control module monitors the negative, or sinking, side of its pumping-current control circuit and sets this code when that circuit reads below its expected range; the code alone does not prove a short to ground.
Common causes
Most likely first.
- Short to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
How to diagnose it
- Save freeze-frame data and check live Bank 1 Sensor 2 readings to establish when the negative current-control circuit goes low.
- Inspect the negative current-control wire and connector for chafing, corrosion, loose terminals, or insulation damaged near the exhaust.
- Use the wiring diagram to check the negative current path for an unintended connection to ground.
- Check connector terminal contact and continuity through the negative current-control wire using the manufacturer's procedure.
- If the harness checks pass, test the sensor and module circuit as directed by the manufacturer's specification.
Common fixes
- Repair chafed or heat-damaged negative current-control wiring.
- Clean or repair corroded or loose connector terminals.
- Repair a confirmed short to ground in the negative current path.
- Replace the sensor or repair the module only if testing confirms an internal fault.
Can I keep driving?
If the engine runs normally and the check-engine light is steady, limit driving and avoid hard acceleration until diagnosed. The fault can disrupt downstream oxygen-sensor control and emissions monitoring, and fuel economy or emissions results may worsen.
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.