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.

Real-world scan data

Seen in

603

scans in the past year

Found in

0.1%

of scans

0.2%

of scans that found faults

Appears alongside · share of P0155 scans

P0161in 47.3% of scans

P0135in 43.5% of scans

P0141in 24.5% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

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.

Read & clear P0155 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX