What it means
The oxygen sensor pumping current trim circuit for bank 2 sensor 1 is above the expected level.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Bank 2 Sensor 1 is the upstream oxygen sensor on the engine's second cylinder bank, and its pumping-current trim circuit lets the module calibrate the exhaust-mixture reading. P2631 sets when that circuit is above its expected level, which can occur with an open trim resistor or a wire shorted to battery voltage.
Common causes
Most likely first.
- Open calibration trim resistor
- Corroded sensor connector
- Supply wire pinched against B+ source
Symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
How to diagnose it
- Record freeze-frame data and check Bank 2 Sensor 1 live data, fuel trims, and related oxygen-sensor codes.
- Inspect the upstream Bank 2 Sensor 1 connector for corrosion, loose or pushed-back pins, and signs of water entry.
- Trace the trim-circuit wiring for a pinch or contact with a battery-positive supply, taking care to distinguish this circuit from the sensor heater wiring.
- Test the calibration trim resistor and circuit continuity using the vehicle wiring information to check for an open circuit or unwanted voltage.
- Compare circuit readings and sensor response with the manufacturer's specification before replacing the sensor or investigating the module.
Common fixes
- Restore proper contact at a corroded or loose Bank 2 Sensor 1 connector.
- Repair a trim-circuit wire shorted to battery voltage.
- Replace an open calibration trim resistor or the sensor assembly if the resistor is not separately serviceable.
- Repair the module circuit only after the sensor and its wiring pass the specified checks.
Can I keep driving?
If the engine runs smoothly, a short gentle trip is generally possible, but the fault can cause poor fuel economy, hesitation, and excess emissions. Avoid extended driving and have the fault repaired before an emissions test.
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.