P0135 — O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)

P0135 means the heater circuit inside your upstream oxygen sensor on Bank 1 has failed. The fix is almost always replacing the O2 sensor itself.

Cost range: $150–$500. Severity: low. Safe to drive? Yes, but you'll see worse fuel economy until fixed.

Most common causes of P0135

1. Failed O2 sensor heater element — Replace the upstream sensor on Bank 1. ($150–$400)
2. Blown O2 sensor fuse — Check fuse before replacing sensor. ($1–$10)
3. Wiring harness damage — Look for melted wires near the exhaust. ($50–$200)

Symptoms drivers report with P0135

• CEL
• Slow oxygen sensor response
• Reduced MPG