What it means
HO2S Heater Control Circuit Low (Bank 2 Sensor 2): the control-circuit voltage is below 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 2 is the heated oxygen sensor after the catalytic converter on Bank 2. Its heater control circuit voltage is monitored by the control module; P0057 sets when that voltage is lower than expected, which can happen if the control wire is shorted to ground or the heater circuit is faulty.
Common causes
Most likely first.
- Heater control circuit shorted to ground
- Heater element or wiring fault
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 look for other low-voltage or heater codes that may reveal a shared supply issue.
- Inspect Bank 2 Sensor 2’s connector and nearby wiring for melted insulation, contact with the exhaust, corrosion, or a wire pinched against ground.
- Using the wiring diagram, test the heater control wire for a short to ground and check the sensor heater element for an internal fault.
- Verify the heater supply and control-side voltage using the manufacturer's procedure, taking care not to damage the module circuit.
- If the wiring tests pass, compare the Bank 2 Sensor 2 heater with the manufacturer's specification to determine whether the sensor has failed.
Common fixes
- Repair chafed Bank 2 Sensor 2 heater wiring that is shorted to ground.
- Clean or repair corroded or damaged terminals at the sensor connector.
- Replace Bank 2 Sensor 2 if its heater element is faulty.
- Repair a confirmed heater supply or control-circuit fault.
Can I keep driving?
Driving is usually possible if the vehicle runs normally, though the sensor may warm slowly and emissions can increase. Have the low-voltage fault checked soon; avoid assuming that replacing the sensor will fix a grounded wire.
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.