P0155
O2 Sensor Heater Circuit Bank 2 Sensor 1
Fuel & air metering / emissions
Generic OBD-II
Medium
What it means
P0155 means the heater circuit in the bank 2, sensor 1 oxygen sensor isn't working as expected. The heater brings the sensor up to temperature quickly so the engine can enter closed-loop fuel control sooner. The car still runs, but you may see slightly worse cold-start economy and an emissions-test failure. A failed heater element inside the sensor is the usual cause.
Medium
Can I keep driving? Safe to drive — the sensor heater just makes the O2 sensor reach operating temperature faster; the car runs normally but may run richer at cold start and can fail emissions.
Common symptoms
What you'll notice
- Check-engine light on
- Slightly worse fuel economy, mainly right after a cold start
- Longer time before the engine enters closed-loop fuel control
- May fail an emissions/readiness test
Common causes
Most likely first
- Failed heater element inside the bank 2 sensor 1 oxygen sensor (most common)Likely
- Blown fuse feeding the sensor heaterCommon
- Open, shorted, or corroded wiring/connector in the heater circuitCommon
- Poor ground for the heater circuitLess often
- Rarely, an ECM/PCM heater driver faultLess often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and check the fuse that powers the O2 sensor heaters.
- Inspect the bank 2 sensor 1 connector and wiring for corrosion, damage, or a poor ground.
- Measure the heater element's resistance at the sensor against spec.
- Verify power and ground reach the heater circuit with the key on.
- Replace the oxygen sensor if the heater element is open. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0155?+
Yes. The heater only speeds up sensor warm-up, so the car drives normally. Expect slightly worse cold-start economy and a possible emissions failure until it's fixed.
Can I just clear P0155?+
It comes back once the heater monitor runs if the element or wiring is still faulty. Check the fuse and wiring first, then replace the sensor if its heater is open.
Related codes
Often seen with P0155
Read & clear P0155 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