P0135Powertrain
Powertrain · SAE
O2 sensor heater circuit (bank 1, sensor 1)
Meaning
The control unit detects a fault in the heater circuit of the upstream oxygen sensor on bank 1. The heater brings the sensor quickly up to operating temperature.
Common causes
- Open or failed sensor heater element
- Blown heater-circuit fuse
- Damaged or corroded heater wiring or connector
- Faulty heater supply relay
- Incorrect heater-circuit ground or supply
Symptoms
- Check-engine light on
- Delayed transition into closed-loop operation
- Slightly higher fuel consumption when cold
- Possible mild increase in emissions during warm-up
Severity
Minor: driving is not affected, but the sensor takes longer to work and fuel use and emissions are slightly worse in the meantime.
What to do
- Measure the sensor heater element resistance and compare it with specification
- Check the heater-circuit fuse and supply relay
- Inspect the heater wiring, connector, ground and supply
- If the heater element is open, replace the upstream oxygen sensor