P0135 Code: O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)
🟢 Low severity · drivable
Safe to drive. This affects only the sensor's warm-up heater, though it may run slightly rich when cold.
What P0135 means
The heater inside the bank 1 upstream oxygen sensor isn't working. Modern O2 sensors have a built-in heater that brings them up to temperature quickly so they start reading accurately sooner after a cold start.
Symptoms
- Check engine light is on
- Possibly slightly rich running when cold
- Usually no noticeable driving symptoms
Common causes
- most common: Faulty oxygen sensor (heater element failed)
- common: Blown fuse or damaged heater circuit wiring
- less common: Corroded sensor connector
How to fix it
| Fix | DIY? | Typical cost |
|---|---|---|
| Check the O2 sensor heater fuse and wiring | Yes | $0–20 |
| Replace the bank 1 upstream oxygen sensor | Yes | $60–200 |
Frequently asked questions
Can I drive with a P0135 code?
Yes. It only affects the sensor's heater, so drivability is unaffected. It may fail an emissions test until fixed.
What is the most common cause of P0135?
A faulty oxygen sensor whose internal heater has failed. Replacing the sensor fixes it.
How much does it cost to fix a P0135?
Typically $60–$200 for a new oxygen sensor.
Related codes
P0141
P0141 Code: O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)
P0130P0130 Code: O2 Sensor Circuit Malfunction (Bank 1 Sensor 1)
P0155P0155 Code: O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)
Updated 2026-08. This page is informational and not a substitute for professional diagnosis.