What does the P0036 OBD-II code mean?

The P0036 code is a diagnostic trouble code indicating that the heated oxygen sensor (HO2S) control circuit bank 1, sensor 2, is not sending the correct data to the powertrain control module (PCM). For the engine to operate correctly, the engine exhaust should have a specific air-fuel ratio of 14.7 to 1, and it’s the HO2S (oxygen sensor) that detects the oxygen from the exhaust. The error code P0036 triggers when there is an ongoing issue with the heater element of the HO2S. The reason it’s heated is to ensure the PCM maintains a high-speed response to the closed-loop system, thereby reducing emissions at startup. 

How serious is the P0036 code?

This diagnostic code is typically considered to be minor-to-moderate. The HO2S plays a small part in determining how a vehicle runs, meaning there are usually very few driveability symptoms. Therefore, the car can continue to be driven but should ideally be taken in for diagnostic and repair as soon as possible to prevent potential issues, including poor operation, decreased fuel economy, sensor loop failing, and damage to other components.

What are the common symptoms of a P0036 trouble code?

Whilst in many cases of OBD-II fault codes triggering, there will be several symptoms expected relating to the issue, with the P0036, this is not the case:

  • Check engine light illuminated
  • Depending on car manufacture PCM programming, different driveability symptoms may occur

What are the causes of a P0036 diagnostic code?

The most common causes for the P0036 trouble code triggering are:

  • Corroded or non-existent exhaust ground
  • Defective wiring to the oxygen sensor (HO2S)
  • HO2S fuse blown due to water ingress
  • Faulty HO2S sensor for the engine bank 1 sensor 2
  • Faulty PCM (very rare)


How to diagnose a P0036 OBD-II code?

Diagnosing an OBD-II fault code is ideally carried out using an OBD-II scanner or by booking a diagnostic check with a trusted garage or mechanic. Following the diagnostic steps fully and correctly is vital for accurate diagnosis. Indeed, it is not uncommon for older vehicles with over 100,000 miles to have momentary sensor issues occur at startup, so resetting the fault code is essential to avoid unnecessary repairs:

  • Investigate to see if there are any technical service bulletins available for your vehicle’s model and make to see if there is a known problem for your car that can help resolve the issue.
  • Scan your system for other OBD-II codes. If present, these must be remedied before proceeding.
  • Clear the fault codes, followed by a test drive of the car while reading the live data on an OBD-II scanner.
  • If the code persists, visually inspect the wiring for damaged or loose wiring (common)
  • Check both power and ground to the HO2S
  • Test the HO2S heater element 


How to fix a P0036 OBD-II trouble code?

It is recommended to test drive the vehicle after each check/work is performed to see if the fault code clears. If the code returns, move on to the next repair. The most common repairs to resolve a P0036 fault code are:

  • Verify the code with an OBD-II scanner, and reset the fault code. Follow this with a test drive of the car to see if the trouble code clears. If it returns:
  • Repair or