P0135 on a Toyota: Causes, Fixes & Repair Cost
🟠 Moderate severity · drivable
Safe to drive, but the sensor warms up slowly, so fuel economy and emissions suffer and the light stays on.
What P0135 means on a Toyota
On a Toyota, P0135 means the heater inside the bank 1 upstream oxygen sensor isn't working. That sensor sits in the exhaust before the catalytic converter and needs its heater to reach working temperature quickly after a cold start. With a dead heater, the sensor reads slowly and the engine may run slightly rich until it warms.
Is P0135 common on Toyotas?
P0135 is common on higher-mileage Toyotas like the Camry, Corolla, and RAV4, where upstream oxygen sensors wear out with age. The heater element inside the sensor is the part that fails most often. It is a straightforward sensor replacement, not a sign of engine trouble.
Commonly reported on: Camry, Corolla, RAV4, Highlander.
Symptoms
- Check engine light is on
- Longer warm-up before the sensor reads correctly
- Slightly worse fuel economy
- Possible failed emissions test
Common causes
- most common: Failed O2 sensor heater element
- common: Blown heater circuit fuse or relay
- common: Damaged or corroded wiring or connector at the sensor
- less common: Defective aftermarket sensor
How to fix it
| Fix | DIY? | Typical cost |
|---|---|---|
| Replace the upstream oxygen sensor | Yes | $80–220 |
| Replace the blown fuse or relay | Yes | $10–40 |
| Repair the wiring or connector | Mechanic | $80–200 |
Frequently asked questions
Other common Toyota codes
P0135 on other brands
Looking for the full (non-brand-specific) guide? See the P0135 code page →
Browse all Toyota codes: Toyota hub →
Updated 2026-08. This page is informational and not a substitute for professional diagnosis.