P0141 O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 2)
The heater in the downstream oxygen sensor — the one after the catalytic converter — has failed.
Oxygen sensors
Identical fault to P0135, but on the sensor downstream of the converter. That sensor's job is monitoring converter efficiency rather than controlling fuelling, so the drivability impact is smaller. It matters mainly because a downstream sensor that can't reach temperature can't run the catalyst monitor — and an unheated, misreading downstream sensor is a well-known way to end up with a false P0420 and a needlessly replaced converter.
Diagnose P0141 on your specific vehicle Add your year, make and model for ranked causes, repair videos and the exact parts you needCan I keep driving?
Driveable
Yes, with essentially no change in how the car drives.
How serious
Low. Emissions failure and a blocked catalyst monitor; the engine drives normally.
Symptoms you'll notice
- Check-engine light with no drivability change
- Failed emissions test, or monitors that won't set ready
- Sometimes a P0420 appearing alongside
What causes P0141
Ordered by what to check first — how likely each cause is, weighed against what it costs to rule out. Working down the list in order is what stops you replacing an expensive part to fix a cheap problem.
Failed heater element
The usual cause. Downstream sensors sit under the car and take more road spray and salt than upstream ones.
Corroded connector or damaged wiring
Because of its location beneath the vehicle, corrosion is especially common here. Inspect thoroughly — this is frequently the whole fault.
Blown fuse
Free to check and sometimes the entire answer.
Physical damage from road debris
The sensor and its harness are exposed underneath and can be struck or snagged.
How to diagnose it
- Check the heater circuit fuse.
- Inspect the sensor and harness underneath the vehicle for corrosion and impact damage.
- Measure heater resistance across the heater pins and compare to spec.
- Confirm battery voltage reaches the heater circuit with the key on.
- If a P0420 is stored too, fix this heater fault first and re-test before considering a converter.
Parts you might need
Tools for the job
- Oxygen sensor socket
- Multimeter
- Jack and stands
- Penetrating oil
Related trouble codes
- P0135 — O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)
- P0420 — Catalyst System Efficiency Below Threshold (Bank 1)
Fitment matters. Causes and parts above are the common cases for P0141 across vehicles. The specific part numbers, procedures and torque specs vary by year, make, model and engine — always confirm against service data for your vehicle before buying parts or starting work.