P0135
O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)
This means the heater inside the oxygen sensor located before the catalytic converter on Bank 1 isn't working, preventing the sensor from reaching its operating temperature quickly.
The Powertrain Control Module (PCM) has detected a malfunction in the heater circuit of the upstream oxygen sensor on Bank 1.
Common causes
- high
Faulty O2 sensor (heater element failure)
The heater element within the O2 sensor is a common failure point due to heat cycles.
Typical part cost: $50-200 part
- medium
Wiring or connector issues to the O2 sensor
Damaged, corroded, or loose wires/connectors can interrupt the heater circuit.
Typical part cost: $0-50 (repair)
See all causes + fix costs
Create a free Wrenchify account to unlock the rest for P0135.
Unlock causesFree forever · No credit card
First things to check
- 1Inspect O2 sensor wiring and connector for damage or corrosion
- 2Check resistance of the O2 sensor heater circuit (unplugged sensor)
Get the full step-by-step diagnosis
Create a free Wrenchify account to unlock the rest for P0135.
Unlock diagnosisFree forever · No credit card
Related codes
See related trouble codes
Create a free Wrenchify account to unlock the rest for P0135.
Unlock related codesFree forever · No credit card
Frequently asked questions
What does 'Bank 1 Sensor 1' mean?
Bank 1 is the side of the engine with cylinder #1. Sensor 1 is the upstream oxygen sensor, located before the catalytic converter.
Will a P0135 code cause my car to fail emissions?
Yes, a P0135 code will almost certainly cause your car to fail an emissions test because the O2 sensor is not functioning correctly to monitor exhaust gases.
Get the full P0135 diagnosis for your vehicle
Year, make, model + step-by-step repair help — free plan included.