Trouble codes › P0135
P0135 O2 Sensor Heater Circuit (Bank 1, Sensor 1)
Oxygen sensors
P0135 means the heater in bank 1's front oxygen sensor isn't working, usually burned out or missing power.
Oxygen sensors only work when hot, so each has a built-in heater. P0135 means the engine computer found a problem with the heater in the front oxygen sensor on bank 1 (before the catalytic converter): usually the heater has burned out or isn't getting power.
Safe to drive. The engine may run a little less efficiently right after a cold start until the sensor warms up from exhaust heat.
Common causes
- A failed heater inside the oxygen sensor (most common)
- A blown fuse for the oxygen sensor heater circuit
- Damaged wiring or a corroded connector near the sensor (it's close to the hot exhaust)
- A problem in the engine computer's heater control circuit (rare)
Symptoms
- Check-engine light
- Slightly worse fuel economy, especially on short trips
- Usually nothing else
Common on: Honda Accord
What to check first
- Check the fuse for the oxygen sensor heaters (your owner's manual or fuse box lid shows which).
- Inspect the sensor's wiring for melted or chafed spots near the exhaust.
- Measure the heater's resistance across its two heater pins with the sensor unplugged and compare with the spec for your sensor (typically a few ohms to around 20).
- Check for power at the heater feed with the key on; if power is there and the heater is open, replace the sensor.
What does P0135 mean on your vehicle?
The likely cause depends on your engine. iRepair researches your exact year, make, model and engine (service bulletins, recalls and owner reports) and tells you what to check first. Your first 3 questions are free.
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Related codes
General guidance for P0135 on most vehicles. Some makers use the same code a little differently; confirm in the service information for your vehicle, put safety first, and see a professional when in doubt.