P0135
Low SeverityO2 Sensor Heater Circuit (Bank 1, Sensor 1)
Emissions System
What Does P0135 Mean?
The heater in the upstream O2 sensor on bank 1 is not working properly. The heater brings the sensor to operating temperature quickly.
Common Fix
Replace O2 sensor
Estimated Cost (DIY)
$30 - $100
Symptoms
- ⚠️Check engine light
- ⚠️Slow warm-up fuel trim
- ⚠️Slightly increased emissions
- ⚠️Failed emissions test
Related Symptoms
Common Causes
How to Diagnose P0135
- 1Check O2 heater fuse
- 2Measure heater resistance (2-30 ohms normal)
- 3Check power and ground at sensor
- 4Replace sensor if heater open
OEM Diagnostic Flowchart
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Related Resources
Repair guides, symptom pages, and wiring diagrams related to P0135.
Related Symptoms
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Open the exact vehicle hub for a repair workflow commonly associated with P0135.
Open the exact vehicle hub for a repair workflow commonly associated with P0135.
Open the exact vehicle hub for a repair workflow commonly associated with P0135.
Open the exact vehicle hub for a repair workflow commonly associated with P0135.
Exact Repair Workflows
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Open the exact repair flow most commonly associated with P0135 on this vehicle.
Open the exact repair flow most commonly associated with P0135 on this vehicle.
Open the exact repair flow most commonly associated with P0135 on this vehicle.
Open the exact repair flow most commonly associated with P0135 on this vehicle.
Related Codes
The oxygen sensor heater circuit on the upstream (pre-cat) sensor of bank 1 has a fault. The heater gets the O2 sensor to operating temperature quickly for proper fuel trim.
The heater in the downstream O2 sensor on bank 1 has failed.
Heater failure in the upstream O2 sensor on bank 2.
Frequently Asked Questions
- Can a heater fault affect the O2 sensor reading?
- Not directly, but the sensor will take longer to warm up. In cold weather, fuel economy suffers during warm-up.
- Do all O2 sensors have heaters?
- All modern vehicles (1996+) have heated O2 sensors. The heater ensures accurate readings from cold start.
Related Repair Guides
If your vehicle has triggered P0135, these DIY repair guides may help: