What it means
Voltage on the intake air oxygen sensor signal line on bank 1 is above the expected window. A drifted or sluggish lambda sensor lets the mixture run lean or rich without correction — fuel economy and emissions suffer immediately.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The Bank 1 intake-air oxygen sensor reports oxygen content through a signal circuit monitored by the control module. This code sets when the signal voltage rises above the expected range, which can happen if the wire contacts battery voltage, the sensor circuit is open, or connector corrosion interrupts the signal.
Common causes
Most likely first.
- Signal wire shorted to B+
- Open intake air O2 sensor
- Connector pins corroded - high contact resistance
Symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
How to diagnose it
- Review freeze-frame data and live Bank 1 sensor readings to determine whether the signal is fixed high or briefly exceeded its expected range.
- Inspect the Bank 1 sensor connector for corrosion, loose or pushed-back pins, and check the harness for damage or contact with a power wire.
- Compare the Bank 1 reading with other available mixture data to determine whether the high value is isolated to this signal circuit.
- Following the wiring diagram, test the signal wire for a short to battery voltage and check for an open between the sensor and module.
- If wiring and connector tests pass, test the Bank 1 sensor for an open or internal fault according to the manufacturer's procedure.
Common fixes
- Repair or replace damaged Bank 1 signal wiring that contacts a power source.
- Restore loose, corroded, or pushed-back connector terminals.
- Repair an open in the Bank 1 sensor signal circuit.
- Replace the Bank 1 intake-air oxygen sensor if it tests open or fails the manufacturer's checks.
Can I keep driving?
A short trip is generally reasonable if the engine runs normally, but avoid heavy acceleration if it hesitates or runs roughly. A persistent high signal can interfere with mixture control, increasing fuel use and emissions and potentially damaging the catalytic converter.
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.