P0031
HO2S Heater Control Circuit Low Bank 1 Sensor 1
Emissions / O2 sensor
Generic OBD-II
Medium
What it means
P0031 means the heater circuit for the upstream (bank 1, sensor 1) oxygen sensor is reading low voltage — usually a short to ground, an open, or a failed heater element inside the sensor. The heater brings the O2 sensor to operating temperature quickly; when it fails, closed-loop fuel control is delayed but the engine still runs normally.
Medium
Can I keep driving? Safe to drive short-term — no immediate mechanical risk, but it will fail an emissions test and slightly hurt cold-start economy.
Common symptoms
What you'll notice
- Check-engine light on
- Slightly worse cold-start fuel economy
- Delayed closed-loop fuel control after start-up
- Failed emissions test
Common causes
Most likely first
- Failed heater element inside the O2 sensor (most common)Likely
- Short to ground or open in the heater wiringCommon
- Blown heater fuse or poor groundCommon
- Corroded or loose connector at the sensorLess often
- Failed PCM driver (rare)Less often
How to diagnose & fix
Work through it in order
- Scan and record freeze-frame data.
- Check the O2 sensor heater fuse.
- Inspect the connector and wiring for a short to ground or an open.
- Measure the heater element's resistance across the sensor terminals against spec.
- Replace the O2 sensor if the heater is open or out of spec; consider the PCM last. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0031?+
Yes, short-term. The heater only speeds up sensor warm-up, so there's no mechanical danger, but the car will fail emissions and warm-up fueling is slightly less efficient.
Can I just clear P0031?+
It comes back within a drive cycle or two until the heater or wiring is fixed. A failed heater element usually means replacing the O2 sensor.
Related codes
Often seen with P0031
Read & clear P0031 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX