P0135: Oxygen O2 Sensor Heater Circuit Malfunction

Diagnostic trouble codes are output by the control module in cars and trucks that are equipped with OBD-II diagnostic capabilities. The trouble code P0135 is a generic powertrain code indicating a problem in the front oxygen sensor on Bank 1, a heated oxygen sensor circuit that decreases time to enter closed loop. It is necessary to use an OBD-II scanner to obtain trouble codes and then check the indicated parts.

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What Does the Code P0135 Mean?

The first letter of every alphanumeric diagnostic code indicates the vehicle system that the ECM detects as being affected. In this case, the letter ‘P’ indicates a generic powertrain code. If the engine control module detects that the oxygen sensor heater circuit is open, short, or draws too much current based on coolant temperature, the onboard computer will output OBD-II diagnostic trouble code P0135. The number 0135 points toward the heated oxygen sensor circuit, specifically Bank 1, Sensor 1.

What Is a Common Error Code P0135 Problem?

An OBD-II diagnostic scan could return code P0135 due to any of the following causes:

  • High resistance in O2 heater element or O2 heater circuit wiring
  • Internal shorts or open heater element
  • Wiring harness open or short to ground

When you start the engine, the engine control module tests the O2 sensor heater circuit. If the ECM detects any delays or failures, it will output diagnostic trouble code P0135.

How Do I Fix P0135?

Fixing problems involving the O2 heater circuit wiring or element resistance may require rewiring or electrical expertise. If you are not experienced in repairing automotive circuits or electrical systems, you may save time, money and hassle by taking your car or truck to a mechanic or dealer.

You may be able to restore O2 heater circuit or heating element function by resolving any shorts, open or high resistance issues. If an open or short has occurred inside the oxygen sensor itself, it will be necessary to replace this part. A malfunctioning O2 sensor can undermine engine efficiency, drive up emissions, and lead lasting problems to develop over time.

What Should You Do Next?

Check the repair manual for your vehicle make and year model to locate the oxygen sensor. Depending on your skill level, you may be able to save money on labor by doing the necessary part testing, repair, or replacement yourself. It may also be possible to save on parts costs by purchasing the necessary components and supplying them to an automotive repair professional.

There are several options for doing follow-up scans to ensure that the problem is resolved. Mechanics have readers in their garages. If you can safely drive or tow a vehicle to AutoZone, free OBD-II scans are available at every store location. You can also get all of the replacement parts and tools you need to fix or replace the oxygen sensor or any other vehicle part or system.

How Do You Find the Right Parts?

Replacing O2 sensor heater circuit components or the O2 sensor itself can call for OEM replacement parts made to fit your vehicle make and model. The specifications of your car or truck can help you find the best parts for the job when browsing or searching for everything you need to complete a repair.

Reconnecting or switching out a faulty external circuit, harness or wiring may clear this code. Faulty circuits within an O2 sensor typically require replacement of the entire sensor unit. Whether you perform repairs on oxygen sensor circuitry yourself or take your vehicle to a mechanic and just purchase replacement parts, a functional O2 sensor can help the engine in your vehicle sustain efficiency and power. You can get the parts you need at your local AutoZone Store. If the job is too big for you, seek out one of our Preferred Shops to help you do the job.

Advice, how-to guides, and car care information featured on and AutoZone Advice & How-To’s are presented as helpful resources for general maintenance and automotive repairs from a general perspective only and should be used at your own risk. Information is accurate and true to the best of AutoZone’s knowledge, however, there may be omissions, errors or mistakes.

Be sure to consult your owner’s manual, a repair guide, an AutoZoner at a store near you, or a licensed, professional mechanic for vehicle-specific repair information. Refer to the service manual for specific diagnostic, repair and tool information for your particular vehicle. Always chock your wheels prior to lifting a vehicle. Always disconnect the negative battery cable before servicing an electrical application on the vehicle to protect its electrical circuits in the event that a wire is accidentally pierced or grounded. Use caution when working with automotive batteries. Sulfuric acid is caustic and can burn clothing and skin or cause blindness. Always wear gloves and safety glasses and other personal protection equipment, and work in a well-ventilated area. Should electrolyte get on your body or clothing, neutralize it immediately with a solution of baking soda and water. Do not wear ties or loose clothing when working on your vehicle.

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