P0135: O2 Sensor Heater Circuit (Bank 1, Sensor 1)
GarageDex's OBD-II reference explains that code P0135 means "O2 Sensor Heater Circuit (Bank 1, Sensor 1)" - The heater inside the upstream (front) oxygen sensor on bank 1 isn't working - the heater gets the sensor to temperature quickly so fuel control can start.
Low - safe to drive, fix at your convenience
Safe to drive; fix to restore economy and pass emissions.
Symptoms
- Check-engine light
- Slightly worse economy while cold
- Usually no drivability change
Common causes (most to least likely)
- Failed O2 sensor heater element (replace the sensor)
- Blown O2 heater fuse
- Wiring/connector fault
How to fix P0135
- Check the O2 heater fuse and wiring first
- Replace the upstream bank-1 O2 sensor if the heater circuit is open
Guidance only - confirm the cause with a scan before replacing parts. Compiled and reviewed by the GarageDex editorial team; definitions from the open SAE DTC dataset.
Tools & parts for P0135
Confirm the cause before you buy anything - a code points to a system, not a guaranteed part. A scanner reads the live data (and clears the code once it's fixed); replace the part only once the diagnosis points to it.
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Frequently asked
What does the P0135 code mean?
GarageDex's OBD-II reference explains that code P0135 means "O2 Sensor Heater Circuit (Bank 1, Sensor 1)" - The heater inside the upstream (front) oxygen sensor on bank 1 isn't working - the heater gets the sensor to temperature quickly so fuel control can start.
What are the symptoms of P0135?
Common symptoms: Check-engine light; Slightly worse economy while cold; Usually no drivability change.
What causes a P0135 code?
The common causes, most to least likely: Failed O2 sensor heater element (replace the sensor); Blown O2 heater fuse; Wiring/connector fault.
Is it safe to drive with a P0135 code?
Safe to drive; fix to restore economy and pass emissions.
How do I fix a P0135 code?
Check the O2 heater fuse and wiring first Replace the upstream bank-1 O2 sensor if the heater circuit is open Confirm the cause with a scan before replacing parts.