Fuel & air metering · Powertrain · generic (SAE-defined)
P0135: O2 Sensor Heater Circuit (Bank 1 Sensor 1)
P0135 means there is a fault in the heater circuit of the bank 1 upstream oxygen sensor, so the sensor cannot warm up quickly after starting.
Standard title per SAE J2012 / ISO 15031-6 · Updated 2026-11-07 · By CarWhere Research
How P0135 sets
The upstream oxygen (O2) sensor has a built-in electric heater so it starts working soon after a cold start. The powertrain control module (PCM) monitors the heater circuit, either by checking current draw or the voltage on the control side, and sets P0135 if the circuit is open, shorted or drawing current outside the expected range. Test methods vary by manufacturer.
Common causes of P0135
Roughly most likely first; the actual cause depends on the vehicle and needs testing to confirm.
- Failed heater element inside the bank 1 sensor 1 oxygen sensor
- Blown fuse in the heater supply circuit
- Open or shorted heater wiring
- Corroded or loose connector
- Faulty heater control driver in the PCM (uncommon)
P0135 symptoms
- Check engine light on
- Slightly worse fuel economy after cold starts
- Usually no drivability symptoms
How P0135 is diagnosed
- Scan for codes; multiple heater codes at once suggest a shared fuse or power feed.
- Check the heater circuit fuse.
- Unplug the sensor and measure heater element resistance; an open reading confirms a failed heater.
- With the key on, verify heater supply voltage at the harness connector.
- Check the ground or PCM control side of the heater circuit for continuity.
Typical fixes for P0135
- Replace the bank 1 sensor 1 oxygen sensor (the heater is not serviceable separately)
- Replace a blown fuse after locating any short
- Repair damaged heater wiring or connector
- Repair or replace the PCM if the heater driver has failed
Replace parts only after testing confirms the cause — a code names the circuit or condition that failed a check, not necessarily the faulty part. We don’t publish per-repair prices; for what households actually spend on upkeep, see car repair costs.
Manufacturer notes
Some manufacturers log upstream heater faults under P0030-series codes or air-fuel ratio sensor heater codes instead; definitions can vary by manufacturer; check factory service information.
Related codes & warning lights
P0135 FAQ
What does code P0135 mean?
P0135 means there is a fault in the heater circuit of the bank 1 upstream oxygen sensor, so the sensor cannot warm up quickly after starting. The standard definition is "O2 Sensor Heater Circuit (Bank 1 Sensor 1)."
Can I drive with a P0135 code?
Yes, the vehicle typically drives normally once the exhaust heats the sensor. Expect slightly higher emissions and fuel use after cold starts, and fix it before an emissions test.
Can I just clean the oxygen sensor to fix P0135?
No. P0135 is an electrical fault in the heater element or its wiring. If the heater element is open, the sensor has to be replaced.
Why do I have heater codes for several sensors at once?
When more than one heater circuit fails at the same time, a shared fuse, relay or power feed is the likely cause rather than several sensors failing together.
Keep researching
Engine guides by brand (known issues, specs)
More fuel & air metering codes
Sources
- SAE J2012 — Diagnostic Trouble Code Definitions (standard code titles)
- ISO 15031-6 — Road vehicles: communication between vehicle and external equipment for emissions-related diagnostics, Part 6: Diagnostic trouble code definitions
- U.S. EPA — Vehicle Emissions Inspection and Maintenance (I/M) programs
- U.S. EPA, 40 CFR 86.1806-17 — Federal onboard diagnostics requirements for light-duty vehicles
- California Air Resources Board — On-Board Diagnostic (OBD) Program
General information written by CarWhere Research, not a diagnosis of your vehicle. Manufacturers can add their own sub-definitions and test conditions; confirm with the factory service information for your year, make and model. Before paying for a repair, check NHTSA for open recalls and your warranty booklet: federal law requires an emissions warranty on major emission-control parts such as the catalytic converter and engine computer.