P0135: O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)
P0135 means the heater inside the upstream O2 sensor failed. The fix is almost always a new O2 sensor.
Severity: moderate · System: Powertrain · Safe to drive: usually, short-term. Fix within a month — sensor is running blind during warm-up.
Symptoms
- Check engine light
- Slightly worse fuel economy
Common causes
- Failed O2 sensor heater
- Blown O2 sensor fuse
- Wiring damage
Fair repair prices
| O2 sensor replacement | $200–$450 |
|---|---|
| Fuse / wiring repair | $60–$200 |
Ranges are US market averages (parts and labor). If your shop's quote is above the high end, ask for a line-item breakdown or run it through the invoice checker.
Other codes
- P0300 — Random / Multiple Cylinder Misfire Detected
- P0301 — Cylinder 1 Misfire Detected
- P0420 — Catalyst System Efficiency Below Threshold (Bank 1)
- P0430 — Catalyst System Efficiency Below Threshold (Bank 2)
- P0171 — System Too Lean (Bank 1)
- P0174 — System Too Lean (Bank 2)
- P0442 — Evaporative Emission Control System Leak (Small)
- P0455 — Evaporative Emission Control System Leak (Large)