What it means
The ECM detects a negative voltage on the signal line of oxygen sensor 2 on bank 2. This is unusual for narrow-band sensors and often indicates a short to a negative reference, ground offset, or a wide-band sensor wired incorrectly.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Bank 2 Sensor 2 is an oxygen sensor downstream of the catalytic converter on the bank 2 exhaust, and its signal helps the ECM monitor catalyst performance. This code sets when the ECM detects a negative signal voltage from that sensor, which is abnormal for a typical narrow-band sensor and can indicate a signal short or ground-reference problem.
Common causes
Most likely first.
- Signal wire shorted to negative reference
- Ground offset between sensor and ECM
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 view the Bank 2 Sensor 2 signal alongside other oxygen-sensor data to confirm the negative reading is specific to this sensor.
- Inspect the Bank 2 Sensor 2 connector and exhaust-area harness for heat damage, moisture, corrosion, or contact with the exhaust.
- Using the wiring diagram, check the signal wire for a short to a negative reference and inspect the sensor and ECM ground paths for voltage offset.
- Verify that the fitted sensor type and wiring match the vehicle configuration, especially if the sensor or exhaust wiring was recently changed.
- Test the sensor signal and circuit using the manufacturer's procedure before replacing the sensor.
Common fixes
- Repair a damaged Bank 2 Sensor 2 signal wire or connector.
- Restore a sound sensor or ECM ground connection.
- Correct a sensor wiring or compatibility error if the wrong sensor type was fitted.
- Replace Bank 2 Sensor 2 if its signal remains negative with the circuit and grounds verified.
Can I keep driving?
A short drive is generally possible if the engine runs normally, but increased fuel use and emissions may continue and the vehicle may fail an emissions test. Address it soon, and stop if the engine develops severe hesitation or stalling.
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.