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
Common Causes
Failed O2 sensor heaterlikely
Blown O2 heater fusepossible
Wiring issuepossible
Corroded connectorpossible
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
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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.