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P1135 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.


P1135 is an OBD-II Code that refers to Air/Fuel Sensor Heater Circuit Response


A P1135 code is caused by an ECM (Engine Control Module) receiving a signal that the air/fuel sensors heater is not within the required temperature range. This code is the result of a lack of change in the sensor readings when it should be responding. As your car’s engine heats up, the effective resistance in the air/fuel sensor heater changes and this signal tells the ECM that it needs to adjust ignition timing and fuel delivery. When this occurs, it will set a P1135 code.


Common causes for this code include:

  • Air/Fuel Sensor Heater Circuit Open 
  • Air/Fuel Sensor Heater Circuit Short To Ground
  • Faulty Air/Fuel Sensor Heater
  • Bad Harness or Connection
  • Faulty ECM


The symptoms of a P1135 code are:

  • The Check Engine Light comes on and stays on
  • The engine does may not run properly
  • No symptoms may be possible


To diagnose a P1135 DTC code, a technician would:

  1. Scan for codes in the ECM
  2. If the code is present, check for poor connections and harness issues
  3. Replace and monitor sensor heater to determine if it’s in correct temperature range 
  4. Once the above steps have been completed, recreate conditions causing code to set 
  5. Also, look for any exhaust leaks near the sensor to ensure that it is not damaged.
  6. Run test drive for 10 minutes at steady speed, with no sudden movements 
  7. Scan again for codes

Common mistakes

The following are some of the most common mistakes that a technician may make when diagnosing a P1135 code:

  • Not checking for faults in harness or connections
  • Not testing after replacing sensor heater 
  • Not recreating conditions that led to the code setting 
  • Not checking for exhaust leaks near air/fuel sensors 
  • Failure to scan first, then test drive. You must first scan before you can test drive

How serious is this?

A P1135 code is not considered to be serious under normal conditions. If you experience any of the symptoms listed above, make an appointment with your local service center to have it checked out. Any damage that is done as a result of this code could lead to further complications if not addressed immediately.

What repairs can fix the code?

repair manuals

The following are solutions that may fix this problem:

  • Replacing Air/Fuel Sensor Heater
  • Replacing Air/Fuel Sensor
  • Resetting the ECM
  • Repairing or replacing harness or connections
  • Testing and replacing associated components (sensors, relays, fuses) 
  • Addressing any leaks near the exhaust of the vacuum.
  • Recreating conditions that cause this code to set. This will vary depending on the problem.

Related codes

A P1135 is related to and may be accompanied by the following codes: 

P0102 – Mass or Volume Air Flow Circuit Malfunction

P0107 – Manifold Absolute Pressure/Barometric Pressure Circuit Low Input

P0108 – Manifold Absolute Pressure/Barometric Pressure Circuit High Input

P1131 – P1135 – Range (MAF) Sensor Issues


In conclusion, the P1135 code is a generic trouble code that means the computer has detected an issue with the air/fuel sensor heater. A P1135 code is usually not serious, but if it occurs frequently, repairs should be made to correct the problem at hand as it has the cause further complications down the road.