Sensors and circuits

P0141Oxygen sensor heater circuit malfunction, bank 1 sensor 2

O2 Sensor Heater Circuit Bank 1 Sensor 2

Get it diagnosed soon

Generic OBD-II code

Oxygen (O2/A:F) Sensor

What this part does

Measures exhaust oxygen content so the control module can trim fuel delivery to maintain the target air-fuel ratio.

What the computer is measuring

Sensor 2 on bank 1 is the oxygen sensor behind the catalytic converter. It has almost nothing to do with running the engine. The front sensor does that. The rear sensor exists to grade the converter, by showing how much the exhaust oxygen level is being smoothed out as it passes through.

Like the front sensor, it only produces a usable signal once it is hot, and it sits further back in the exhaust where gas has already given up much of its heat. That makes it more dependent on its built in electric heater than the front sensor is, which is a large part of why rear heater failures are so common.

P0141 means the computer commanded that heater and the current it measured was not what a healthy element draws. It is a circuit fault, not an oxygen reading fault.

Nothing about this changes how the car drives, because the fuelling is controlled by the front sensor. What it does block is the catalyst efficiency monitor. That test needs a working rear sensor to run at all, and it is one of the readiness monitors an emissions test checks for. So a vehicle with P0141 will fail an inspection twice over: once for the stored code and the illuminated light, and again because the monitor sits incomplete.

Before condemning the sensor, look at what else is stored. Several vehicles run all the sensor heaters from one fuse, and one blown fuse produces several codes that look like several dead sensors.

What you will notice

  • Steady check engine light, usually within a minute or two of starting.
  • No change in how the vehicle drives.
  • An emissions test failure, because the catalyst monitor cannot complete.
  • Sometimes stored together with P0135 when a shared fuse has blown.

Likely causes, most common first

Ordered by how often each one actually turns out to be the problem, not alphabetically and not by part price.

  1. A failed heater element inside the downstream sensor

    The most common cause. The rear sensor sits further back in the exhaust where it runs cooler and relies on its heater more, so it often fails before the front one.

  2. A blown fuse on the shared heater circuit

    Check this first. It costs nothing and it explains the code immediately when more than one heater code is stored.

  3. Corroded wiring or connector at the sensor

    The rear sensor connector is usually the most exposed one on the vehicle, sitting under the floor in the road spray.

  4. Damage to the sensor harness from exhaust heat or road debris

    Melted insulation against the exhaust pipe and chafed wire against a heat shield are both common finds.

  5. A failed relay or computer driver on that circuit

    Uncommon, and only worth reaching after the sensor, fuse and wiring have been checked.

What to check, in order

  1. Check whether P0135 or other heater codes are stored alongside it.

    Several heater codes together means a shared fuse or relay, not several failed sensors. One code alone isolates the fault to that sensor and its own wiring.

  2. Check the oxygen sensor heater fuse.

    A blown fuse explains the code. Find the short that blew it before fitting a new one.

  3. Inspect the sensor wiring where it runs along the exhaust and past heat shields.

    Melted or chafed insulation explains the fault and repairing the wire may save the sensor.

  4. Measure the heater element resistance at the sensor connector.

    An open circuit means the sensor is finished. A normal low resistance reading means the heater is intact, so the fault is in the supply, the ground or the computer driver.

Where this one turns up most

  • Higher mileage vehicles on original sensors, where the rear one commonly fails first.
  • Vehicles in salted winter climates, where the underfloor connector corrodes.

Codes that often show up alongside it

What a DriveDecode adapter can read

A DriveDecode adapter reads engine and emissions systems: the powertrain and emissions codes the OBD-II standard requires on every US vehicle it covers. It does not read ABS, airbag (SRS), TPMS or transmission-specific manufacturer codes. Those need make-specific decoding that generic OBD-II hardware cannot do.

Reading P0141 on your own car

DriveDecode pulls P0141 straight off the vehicle along with the freeze frame the computer stored when it set: the coolant temperature, engine load and speed at that exact moment. That context is what separates a fault that happens on a cold start from one that happens under load, and it is the first thing the list above asks you to narrow down.

See how DriveDecode works

Last reviewed 2026-09-05. Definition sourced from the published standard.