Severity: Low
Safe to drive. Schedule a diagnosis soon.
What P0135 means
The heater inside the upstream bank 1 O2 sensor is not working, so the sensor takes longer to start reading after a cold start.
Symptoms
- Usually none
- Slightly worse cold-start economy
Common causes
Most likely first
- 1Failed O2 sensor heater
- 2Blown heater fuse
- 3Wiring damaged by exhaust heat
How we diagnose it
- Check heater fuse
- Measure heater resistance and supply
Every vehicle sets codes under its own conditions. We check the factory diagnostic steps and service bulletins for your VIN, so the repair targets the actual cause.