P0155 O2 Sensor Heater Circuit (Bank 2 Sensor 1)
P0155 is a generic OBD2 powertrain code. It means “O2 Sensor Heater Circuit (Bank 2 Sensor 1)” — the same on every make and model, because the definition comes from the SAE J2012 standard rather than from the carmaker.
Ask the AI about P0155 on your car- System
- Powertrain (P)
- Code type
- Generic (SAE)
- Range
- P01xx
- Urgency
- Low
What P0155 means
Oxygen sensors have a built-in heater so they start working within seconds of a cold start. The computer found the heater circuit of the bank 2, sensor 1 oxygen sensor drawing the wrong current, or none at all.
Symptoms
- Usually nothing but the lamp
- Slightly worse fuel economy on short trips
- A failed emissions inspection
Most likely causes
- The heater element inside the sensor has burnt out — the sensor is replaced as a unit
- A blown heater fuse
- A chafed wire or corroded connector near the hot exhaust
What to check first
- Check the fuse for the oxygen-sensor heaters first
- Measure the heater’s resistance at the sensor connector — typically a few ohms; an open circuit means a failed heater
- Make sure the new sensor matches the position in the code: bank 2, sensor 1
Can I keep driving with P0155?
Safe to drive — fix it when convenient
Yes. Until the sensor warms up on its own the engine runs on a default mixture — a little rich and thirsty. Fix it when convenient.
What the wording tells you
The wording names a fault in the component’s circuit without saying more. Check the connector, the wiring and the fuse, and test the component, before replacing it.
Bank 2: engines with two rows of cylinders — V6, V8, boxer — have two banks. Bank 1 is the side that holds cylinder 1, bank 2 the other side; an inline engine has only bank 1.
Sensor 1: exhaust sensors are numbered along the exhaust flow. Sensor 1 is the one nearest the engine — for oxygen sensors, the one before the catalytic converter — and each higher number sits further downstream.
How P0155 breaks down
Powertrain. Engine, transmission, fuel and emissions — the codes behind the check engine lamp.
Generic code: defined by SAE, the same on every make.
Fuel & air metering.
The specific fault within this range.
Where to look: Fuel & air metering
The sensors the engine computer meters fuel from — mass air flow, manifold pressure, intake air and coolant temperature, throttle position, oxygen sensors and fuel pressure — the fuel trims it learns from them, and the injector, fuel-pump and turbocharger circuits.
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Frequently asked
What does P0155 mean?
P0155 is a generic OBD2 powertrain code. It means “O2 Sensor Heater Circuit (Bank 2 Sensor 1)” — the same on every make and model, because the definition comes from the SAE J2012 standard rather than from the carmaker. Oxygen sensors have a built-in heater so they start working within seconds of a cold start. The computer found the heater circuit of the bank 2, sensor 1 oxygen sensor drawing the wrong current, or none at all.
Can I drive with P0155?
Yes. Until the sensor warms up on its own the engine runs on a default mixture — a little rich and thirsty. Fix it when convenient.
What causes P0155?
The heater element inside the sensor has burnt out — the sensor is replaced as a unit; A blown heater fuse; A chafed wire or corroded connector near the hot exhaust.
How do I clear P0155?
Fix the cause first, then clear it with any OBD2 scanner or app. Once the fault is gone the car also clears it on its own: the check engine lamp goes off after the self-test passes on three drive cycles in a row, and the stored code ages out after about 40 warm-ups. Clearing without a repair only hides it for a while — and resets the readiness monitors an emissions inspection looks at.
Is P0155 the same on every car?
Yes. P0155 is a generic SAE J2012 code, so its definition is identical on every make and model. What differs is the cause behind it and the repair procedure, which depend on the engine — that’s why the assistant on this page asks for your car.
Guides
Definitions: the generic SAE J2012 codes from Brimly’s offline dictionary (data version 2026.09). Causes and advice are general guidance for all makes — the service information for your car has the last word.