Trouble code · Powertrain · Generic (all makes)

P0135 O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)

The heater inside the upstream oxygen sensor on bank 1 isn't working. The heater helps the sensor start working quickly after a cold start.

Safe to drive?
Usually OK to drive
Get it checked soon
Scanner you need
Any OBD2 scanner
Even a basic code reader shows it
NHTSA complaints quoting it
4
Vehicle complaints, 2015–2025

Common causes

  • Failed heater element in the oxygen sensor
  • Damaged wiring or connector
  • Blown fuse

Symptoms

  • Usually none besides the check engine light
  • Slightly worse fuel economy

Can I drive with it?

Safe to drive. Fix it before your next emissions test.

Tip: Replacing the sensor is the usual fix – check the fuse and connector first.

Which scanner reads it?

Any OBD2 scanner reads it.

Budget tools like the ANCEL AD310 read it; tools with live data and graphing – like the BlueDriver or OBDLink MX+ – help you find the cause. Not sure which fits you? Try the Find My Scanner quiz.

In the data

How common is it? In New York City’s taxi and for-hire fleet – high-mileage cars, mostly hybrids – P0135 was the #20 code found on cars failing inspection in 2020–21 (0.7% of codes found).

Of the vehicle complaints owners filed with NHTSA from 2015 to 2025, 4 quote P0135 – most often from Chevrolet, Mercury owners. Complaints lean toward serious problems, so treat this as a sign of how often the code turns up in real reports, not how often cars get it.

Both sources are compared on the Trends page.

General information to help you understand a code – not a diagnosis. Your car’s service information or a qualified mechanic has the final word. See how we research.