P0031 – HO2S Heater Control Circuit Low (Bank 1 Sensor 1)
The P0031 diagnostic trouble code (DTC) indicates that the Engine Control Module (ECM) has detected a low voltage or low current condition in the Heated Oxygen Sensor (HO2S) heater control circuit for Bank 1 Sensor 1. This oxygen sensor is located upstream of the catalytic converter and uses an internal heater to reach operating temperature quickly, improving fuel control and reducing emissions.
Symptoms of P0031
- Check Engine Light illuminated.
- Increased fuel consumption.
- Poor engine performance during cold starts.
- Rough idle until the engine warms up.
- Higher exhaust emissions.
- Delayed closed-loop fuel control.
Common Causes
- Faulty Bank 1 Sensor 1 oxygen sensor heater.
- Open circuit or high resistance in the heater wiring.
- Blown heater fuse.
- Loose, corroded, or damaged electrical connector.
- Poor ground connection.
- Faulty ECM (rare).
How to Diagnose P0031
- Scan for additional diagnostic trouble codes.
- Inspect the oxygen sensor connector and wiring.
- Check the heater circuit fuse.
- Measure the heater element resistance with a multimeter.
- Verify battery voltage and ground at the heater circuit.
- Replace the oxygen sensor if the heater element is defective.
Possible Repairs
- Replace the Bank 1 Sensor 1 oxygen sensor.
- Repair damaged wiring or electrical connectors.
- Replace a blown fuse.
- Repair an open or high-resistance circuit.
- Replace the ECM only after confirming all other components have been tested.
Can You Drive With Code P0031?
Yes, the vehicle can usually be driven with code P0031, but repairs should be made as soon as possible. A failed heater circuit can increase fuel consumption, emissions, and reduce engine efficiency during cold starts.
Estimated Repair Cost
- Oxygen sensor replacement: $100–$350
- Wiring repair: $50–$200
- Fuse replacement: $10–$30
- ECM replacement (rare): $500–$1,500
Related Trouble Codes
- P0030 – HO2S Heater Control Circuit (Bank 1 Sensor 1)
- P0032 – HO2S Heater Control Circuit High (Bank 1 Sensor 1)
- P0036 – HO2S Heater Control Circuit (Bank 1 Sensor 2)
- P0135 – O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)
- P0141 – O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)