What it means
The reference-voltage circuit for the oxygen sensor at Bank 1 Sensor 1 is open or malfunctioning. The code identifies a circuit fault; its effect on measurement depends on the sensor and control system.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The upstream wide-band oxygen sensor on bank 1 uses a reference voltage as part of its exhaust mixture measurement, and the engine control module monitors that reference circuit at Sensor 1. This code sets when the reference circuit is open or otherwise not functioning as expected, so the module may not be able to trust the sensor signal.
Common causes
Most likely first.
- Reference voltage line open
- Wide-band sensor failed
Symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
How to diagnose it
- Read freeze-frame data and Bank 1 Sensor 1 live data to see whether the reference-related fault is constant or occurs only under particular conditions.
- Inspect the Bank 1 Sensor 1 connector and harness for a disconnected plug, pulled wire, corrosion, or heat damage.
- Check the reference-voltage wire for an open between the sensor connector and the module using the vehicle wiring diagram.
- Verify connector pin fit and circuit continuity against the manufacturer's specification, checking for a break that appears when the harness is moved.
- If the reference wiring is intact, test the wide-band sensor and its reference output circuit using the manufacturer's procedure.
Common fixes
- Reconnect the Bank 1 Sensor 1 plug or repair a loose terminal.
- Repair an open or heat-damaged reference wire.
- Replace the Bank 1 Sensor 1 wide-band sensor if it fails the specified test.
- Repair the module reference circuit only if testing isolates the fault there.
Can I keep driving?
The vehicle may be drivable, but fuel economy, idle quality, or emissions can suffer because the upstream bank 1 mixture reading may be unreliable. Avoid extended driving if it runs poorly, and repair the fault before an emissions inspection.
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.