P0036
HO2S Heater Control Circuit (Bank 1 Sensor 2)
Low· Fix when convenientDIY friendlyPowertrainGeneric, all makes
What it means
The ECU has detected a fault in the circuit it uses to switch the oxygen sensor heater at Bank 1 Sensor 2. This is the downstream oxygen sensor on bank 1, mounted after the catalytic converter. Its main job is to check that the converter is working.
Is it safe to drive?
Safe to drive. It mainly affects emissions and cold-start economy.
Symptoms
- Check engine light on
- Slightly worse fuel economy after cold starts
Probable causes
Most likely first
- 1Heater element open inside the sensor
- 2Blown heater fuse
- 3Open or shorted heater control wire
- 4ECU heater driver fault (rare)
How to diagnose it
Work through these in order before buying parts
- 1Record the code and its freeze frame data (speed, load, temperature when it set), then clear it and see if it comes back.
- 2Check the heater fuse.
- 3Measure heater resistance at the sensor (typically 2–20 Ω).
- 4Check for battery voltage on the heater feed with the key on.
- 5Check for technical service bulletins (TSBs) or software updates for your make and model; some codes have known factory fixes.
Common fixes
- Replace the oxygen sensor
- Repair heater wiring or fuse
This information is general guidance for all makes. Exact causes, specifications and procedures vary by vehicle, so confirm with your service manual or a qualified mechanic before replacing parts.