What it means
HO2S Heater Control Circuit High (Bank 2 Sensor 1): the control-circuit voltage is above the expected range. The heater brings the oxygen sensor to operating temperature for closed-loop fuel control.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Bank 2 Sensor 1 is the heated oxygen sensor upstream of the catalytic converter on the second engine bank. This code sets when voltage in its heater control circuit is higher than expected, which can result from a wire shorted to supply or a faulty connection.
Common causes
Most likely first.
- Heater wire shorted to supply
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- Check-engine light on
- Oxygen-sensor heater may warm slowly
- Fuel economy may decrease
- Emissions may increase
How to diagnose it
- Record freeze-frame data and check Bank 2 Sensor 1 heater status and readiness after a cold start.
- Inspect the sensor connector and harness for pinched insulation or contact with a battery-positive feed.
- Check the heater circuit fuse, connector pins, and supply connections using the wiring diagram.
- Test the heater control circuit for a short to supply and poor terminal contact following the manufacturer's procedure.
- Test the Bank 2 Sensor 1 heater element and control circuit against the manufacturer's specification before replacing the sensor.
Common fixes
- Repair wiring pinched against a power source.
- Clean or repair damaged Bank 2 Sensor 1 heater connector terminals.
- Restore a damaged heater circuit connection and secure the harness.
- Replace Bank 2 Sensor 1 if its heater fails the specified test after circuit faults are ruled out.
Can I keep driving?
You can usually drive gently, but a heater fault can delay closed-loop fuel control and increase fuel use and emissions. Arrange repair soon, especially if the engine runs poorly or the warning light flashes.
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.