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P0036 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.


P0036 is the code for the Heater Oxygen Sensor Control (HO2S) Circuit (Bank 1, Sensor 2) which means there is an ongoing problem with the heater element of the HO2S. 


 For the vehicle’s fuel system to operate properly, the engine exhaust system should have a specific air/fuel ratio of 14.7 to 1 as required by the heated oxygen sensors (HO2S), which detects the oxygen content of the exhaust. Heated Oxygen Sensors (HO2S) or Oxygen Sensors (O2S) need to arrive at the minimum operating temperature of 570 degrees Fahrenheit to produce an exact voltage signal. The quicker the HO2S sensor reach that temperature the sooner the sensor will start sending an exact signal to the Engine Control Module (ECM).

In order to meet the required temperature, a heater element is included inside the heated oxygen sensor. This sensor data is calculated by the Engine Control Module (ECM) to adjust the correct amount of fuel delivered to the engine as per the manufacturer specifications

 A large number of the leading car manufacturers use this code definition for the same purpose (such as Mazda, Ford, Nissan, Honda, Kia, Hyundai, Jaguar, Chevrolet, Toyota, BMW, and Audi). Still, it’s crucial to check your vehicle  make and model or repair manual for the exact  definition of the P0036 code, before you assume it’s applicable to your vehicle.


Even though the P0036 code is a generic code, which means it applies to a variety of vehicles with on-board diagnostics, the reasons for its  trigger by the PCM varies from one vehicle to another. 

A P0036 on a Mazda may differ from one on a Ford in terms of which component is causing the issue and various other factors which may affect includes, the component layout, and the overall design of the vehicle.

Some of the possible causes for the error code P0036 are mentioned beneath: 

  • Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2 may be short
  • Exhaust system ground strap may be worn or corroded
  • Fault in Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2
  • Malfunctioning of Engine Control Module (ECM)
  • Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2 circuit wiring failure
  • Heated Oxygen Sensor (H2OS) has high resistance


Below mentioned are the common symptoms related to OBD error code P0036:

  • Check Engine Light will turn ON
  • Decrease in engine performance
  • Decrease in catalytic converter efficiency
  • Increase in fuel consumption
  • PCM entering the failsafe mode, resulting in few drivability issues
  • Emission test failure of the vehicle


In order to diagnose OBD error code P0036, you will need an OBD-II scanner. Firstly, you should reset the OBD-II code and test drive the vehicle to assess if the code appears again. If it returns, you need to  check the voltage from the fused battery feed to the heating element. If there is no voltage, you need to fix the open or short in the circuit. Look for blown fuses that may need replacement. If the circuit is working, you probably need to replace a bad Heated Oxygen Sensor.  Most of the problems related to this code are wiring-related due to the excessive heat of the exhaust damaging other components.

Common Mistakes

There are chances that while diagnosing this code you commit the mistake of replacing the HO2S before checking all the related wiring and the connectors closely. You should ensure there are 12 volts power to the sensor and the ground is good. You should check both sides of the connector wiring to ensure that the connector is good and not damaged.

Often times people make the mistake of diagnosing code P0036 directly after using their vehicle. Given that the exhaust system will be very hot, you should always wait for your vehicle to cool down before you start diagnosing any problems.

How Serious is This?

The DTC code P0036 will usually be preceded by the Check Engine Light coming on the vehicle’s dashboard while it is in operation. The vehicle can still be driven but it should properly be diagnosed at the earliest to prevent potential problems like the sensor loop failure, excessive fuel consumption, poor operation, or damage to other components.

Oftentimes, if the Check Engine Light illuminates immediately at start-up, the OBD-II system can be reset and the vehicle will operate normally.

What Repairs Can Fix the Code

repair manuals

The most common repairs to address the DTC code P0036 are as follows:

  • Firstly, inspect the oxygen sensor wiring for damaged or loose wiring to the sensor.
  • Unplug the oxygen sensor and utilizing a digital volt ohm meter (DVOM) set to the ohms scale, test the resistance of the heater circuit using a wiring diagram for reference. The heater circuit inside the sensor should have some resistance present, in case there is excessive resistance or  is above the limit,   it indicates that there is an open circuit in the heating element  and the oxygen sensor needs to be replaced.
  • Back-test the ground wire at the connector and check for resistance between a notable ground and the connector to the oxygen sensor.
  • Back-test the power supply wire at the connector with the DVOM set to DC volts with the positive lead on the power supply wire and the negative lead at a notable ground to check for power to supply at the oxygen sensor. If no power is present at the connector during the initial car startup (cold start), there might be a problem with the power supply circuit to the oxygen sensor or  the PCM itself.

Related Codes

P0037 – HO2S  Heater Control Circuit Low (Bank 1 Sensor 2)

P0038 – HO2S Heater Control Circuit High (Bank 1 Sensor 2)

P0135 – O2 Heater Circuit (Bank 1, Sensor 1)

P0141 – O2 Heater Circuit (Bank 1, Sensor 2)

P0155 – O2 Heater Circuit (Bank 2, Sensor 1)

P0161 – O2 Heater Circuit (Bank 2, Sensor 2)


The OBD-II scanner error code P0036 is not something that can be ignored. P0036 code, if unresolved for an extended period could cause significant damage to your engine or other components of your vehicle. In some cases, you may also find that an unfixed P0036 code can result in a substantial increase in fuel consumption.

P0036 Code – What Does It Mean & How To Fix It