OBD codes / P0155
P0155
ModerateO2 Sensor Heater Circuit (Bank 2, Sensor 1)
P0155 is safe to drive with — it mainly affects warm-up fueling and emissions, not whether the car runs. Fix it at your convenience, but note it will fail an emissions test. Check the fuse and wiring before buying a sensor.
What this code means
P0155 is the Bank 2 twin of P0135: the heater circuit in the upstream oxygen sensor on the other cylinder bank (the side with cylinder 2) isn't drawing the right current. Oxygen sensors have a built-in heater so they reach operating temperature quickly after a cold start. Almost always the sensor's own heater element has failed, so replacing the sensor is the usual fix — but a blown fuse or a wiring fault can cause it too. It only applies to V6/V8/V-style engines with two banks.
Symptoms you might notice
- Check-engine light, often with no drivability change
- Slightly worse fuel economy, especially on short trips
- Possible failed emissions test
What it costs to fix
Typical range: $150–$450 · about ~0.3–1 hrs of labor
| If the cause is… | Part | Labor |
|---|---|---|
| Upstream oxygen (O2) sensor | $50–$250 | ~0.3–1 hrs |
| Fuse | $1–$10 | ~0.1–0.3 hrs |
| Wiring / connector repair | $10–$120 | ~0.5–1.5 hrs |
The sensor is the usual fix, a low-hundreds job. Check the cheap things first — a blown fuse or chafed wire occasionally causes it for almost nothing. OEM sensors on some makes cost more than aftermarket.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P0155 for my exact vehicle →
Frequently asked
Can I drive with P0155?
Yes — it's a low-urgency code affecting emissions and warm-up fuel economy. The car runs normally; just fix it before an emissions test.
Is P0155 the same as P0135?
Same fault, opposite bank: P0135 is the upstream sensor's heater on Bank 1, P0155 is the upstream sensor's heater on Bank 2 (the cylinder-2 side). Diagnosis and repair are identical.
Does P0155 mean a new O2 sensor?
Usually — the failed heater is inside the sensor, so the sensor gets replaced. Check the fuse and wiring first in case one of those cheap items is the cause.
How much does it cost to fix P0155?
Typically a low-hundreds repair if it's the sensor. Less if it's a fuse or wiring fix. A seized or hard-to-reach sensor adds labor.
Seeing P0155 on your car? Get a diagnosis specific to your exact year, make and model.
Diagnose P0155 for my vehicleGeneric OBD-II reference. Manufacturer-specific behavior varies — confirm with a scan tool and, for safety-related codes, a professional inspection.