P0135O2 Sensor Heater Circuit Bank 1 Sensor 1
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- The upstream oxygen sensor on bank 1 (sensor 1) has an electric heater so that it reaches its working temperature of about 300 °C soon after a cold start. The control module switches the heater on the ground side and checks driver voltage and heater current: GM fails it outside 0.3–2.5 A (or 3.1 A) and calls it 'heater performance', Ford outside roughly 0.22–0.465 A minimum to 3 A, Saab Trionic outside 0.5–2.3 A for 5 s. Manufacturers split heater faults differently between P0030–P0032, P0053 and P0135. With the heater dead, closed-loop control starts late after a cold start. If P0135 and P0141 appear together, check the shared fuse.
- What you may notice
- Check engine light on
- Longer cold-start phase without mixture control, more fuel and emissions
- Follow-up codes P0133/P0134 possible (cold sensor)
- Likely causes
- LikelyHeater element of the sensor burnt out (sensor must be replaced)
- PossibleFuse or relay of the heater supply faulty
- PossibleHeater wiring or connector open, corroded or shorted
- RareUnsuitable replacement sensor (different heater resistance)
- RareHeater driver in the control module faulty
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €5 – €300
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.