Code
P0135
Emissions
Oxygen sensor heater circuit malfunction — Bank 1 Sensor 1
The O2 sensor heater is not working, slowing warm-up and risking emissions failure.
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Most likely causes
- Blown heater element
- Blown fuse
- Wiring fault
Symptoms you may notice
- Check engine light
- Slow warm-up to closed loop
Checks to run
- Test heater circuit resistance
- Check fuse and wiring
Tools you may need
Multimeter
OBD-II scanner
Always diagnose before replacing. Codes share symptoms; confirm the cause with measurements before buying parts.