What it means
The bank 1 sensor 2 oxygen sensor reference voltage 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 its reference-voltage circuit and sets this code when the voltage falls below the expected range; the code alone does not prove a short to ground or show how the mixture is affected.
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 readings for Bank 1 Sensor 2 to confirm when the low-circuit fault is present.
- Inspect the downstream sensor connector and harness for corrosion, pushed-back pins, or insulation rubbed through against the chassis or engine.
- Use the wiring diagram to identify the reference circuit and check for a short to ground before disturbing the harness.
- Check connector terminals for corrosion or poor contact that could create excessive resistance.
- Test reference-circuit continuity and sensor operation using the manufacturer's procedure and specification.
Common fixes
- Clean or repair corroded Bank 1 Sensor 2 connector terminals.
- Repair chafed wiring and protect it from further contact.
- Repair a confirmed short to ground in the reference circuit.
- Replace the downstream sensor if it fails the manufacturer's tests.
Can I keep driving?
If the engine runs normally and the check-engine light is steady, limit driving to necessary trips and avoid hard acceleration until diagnosed. The fault can impair emissions monitoring and fuel economy, and may cause an emissions-test failure.
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.