What it means
The heater current of the intake air O2 sensor on bank 1 does not match the commanded value within tolerance.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The heater in the Bank 1 intake-air oxygen sensor brings the sensing element up to temperature, and the control module checks whether heater current matches its command. This code sets when that current response is outside the expected range, which may result from a drifting heater element, a resistive connector, or an aged sensor.
Common causes
Most likely first.
- Heater element resistance drifted
- High-resistance contact in connector
- Sensor element aged beyond calibration window
Symptoms
- Check engine light on after several drive cycles
- Slightly increased fuel consumption during cold start
- Delayed entry into closed-loop fuel control
- Failed emissions inspection (lambda readiness)
How to diagnose it
- Review freeze-frame and readiness data to see when the Bank 1 heater performance fault occurred, especially after a cold start.
- Inspect the Bank 1 sensor heater connector and wiring for corrosion, looseness, heat damage, or strain.
- Compare commanded heater operation with available current or status data on a scan tool during a cold start.
- Measure heater-circuit resistance and check for voltage drop across the connector and wiring against the manufacturer's specification.
- If the circuit connections are sound, test the Bank 1 sensor heater element and replace the sensor only if it falls outside the manufacturer's specification.
Common fixes
- Clean and secure a high-resistance Bank 1 heater connector.
- Repair damaged or resistive wiring in the Bank 1 heater circuit.
- Replace the Bank 1 intake-air oxygen sensor if its heater resistance or current response is out of specification.
- Clear the code and confirm the heater monitor completes after a cold start.
Can I keep driving?
Driving is generally possible if the engine runs normally, though cold-start fuel use may rise while the sensor warms slowly. The heater fault can delay closed-loop control and prevent the oxygen-sensor readiness monitor from completing.
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.