P0135

O2 Sensor Heater Circuit Bank 1 Sensor 1

Emissions / O2 sensor Generic OBD-II Medium

What it means

P0135 means the ECM detected a fault in the heater circuit of the upstream oxygen sensor on bank 1 (the sensor before the catalytic converter). That heater brings the sensor up to operating temperature quickly so the engine can enter closed-loop fuel control sooner. The car drives normally, but until it's fixed the engine runs in open loop longer, hurting fuel economy and emissions.

Medium

Can I keep driving? Safe to drive — the car runs normally, but it stays in open loop longer, hurting economy and emissions until the sensor's heater is fixed.

Real-world scan data

Seen in

4,758

scans in the past year

Found in

0.8%

of scans

1.3%

of scans that found faults

Appears alongside · share of P0135 scans

P0683in 19.9% of scans

P0141in 19.5% of scans

P0110in 15.0% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Check-engine light on
Slightly worse fuel economy (delayed entry into closed-loop fuel control)
Failed emissions/readiness test

Common causes

Most likely first

Failed heater element inside the upstream (bank 1, sensor 1) O2 sensor — most commonLikely
Damaged wiring or a corroded connector at the sensorCommon
Blown fuse or failed relay feeding the heater circuitCommon
Open or short in the heater ground/control side, or rarely the ECMLess often

How to diagnose & fix

Work through it in order

Check the fuse and relay that supply the O2-sensor heater first — the cheapest possible cause.
Measure the heater element's resistance across its two heater pins and compare to spec; an open reading means a bad sensor.
Inspect the connector and wiring for corrosion, melting, or breaks near the exhaust.
Replace the upstream O2 sensor if the heater is open, then clear and re-test.

FAQ

Quick answers

Is it safe to drive with P0135?+

Yes. The engine still runs and drives normally; the heater fault just slows how fast the sensor reaches operating temperature, so fuel trim and economy suffer slightly. It won't leave you stranded.

Can I just clear P0135?+

It will return once the ECM re-tests the heater, usually within a drive cycle or two. The fix is repairing the circuit or replacing the sensor, not clearing the code.

Read & clear P0135 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX