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P0037 OBD Fault Code (Causes & Fixes)

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Last Updated on: 7th September 2023, 12:35 am

The P0037 fault code stands for: HO2S Heater Control Circuit Low (Bank 1, Sensor 2)

It’s generated when the ECU detects a signal voltage from the bank 1 oxygen sensor 2 that is not within the specified range.

This DTC is minor-moderate in severity, the vehicle can still be driven but should be repaired as soon as feasible.

In this article, we’ll explain what the P0037 OBD fault code means, its signs and causes, and how to fix it.

What Does P0037 Mean?

When the ECU attempts to manage the heater control circuit for Bank 1 Sensor 2 but identifies an elevated voltage situation, it triggers the P0037 code.

The engine needs an optimal air-fuel ratio of 14.7:1 for proper operation.

To monitor and ensure this air-fuel ratio is met, the HO2S (oxygen sensor) evaluates the oxygen content in the exhaust.

The heating of the oxygen sensor is used to accelerate the response within the closed-loop system, thereby reducing emissions during startup.

If an issue arises with the heating element of the HO2S, resulting in high voltage outside the pre-determined range, it results in the error code P0037.

How Serious Is It?

A P0037 OBD fault code is rated as minor to moderate in severity.

Because the HO2S has a very small influence in how the engine operates, there are usually few drivability issues associated with this code.

Therefore, the vehicle may be driven still, but it should be repaired as soon as possible. Always verify this code is real by using a high-quality OBD scanner.

If this fault code is left unfixed for an extended period of time you may encounter the issues listed below.

  • poor performance
  • lower fuel efficiency
  • sensor loop failure
  • potential damage to other components

Signs & Symptoms

A P0037 fault code may not result in many, or any, noticeable issues. It’s likely to be found by mistake when running an OBD system scan.

However, in some cases you may notice the following:

  • The check engine light may come on
  • Reduced performance and drivability
  • Lower fuel efficiency

Possible Causes

Below are the most common causes of a P0037 trouble code.

  • Engine bank HO2S sensor failure 2
  • Exhaust ground connection that is damaged, corroded or loose
  • Faulty sensors
  • Faulty wiring to the oxygen sensor (HO2S)
  • Water ingress causing the HO2S fuse to fail

It’s common for vehicles with over 80,000-100,000 miles to have sensor faults that arise at start-up or during sustained driving.

Diagnosing

You should use a compatible and advanced OBD scanner to verify the P0037 code is the issue.

  1. Check to see if there are any technical service bulletins (TSBs) available for your vehicle to see if there is a known problem with that may help in resolving the issue.
  2. Scan the OBD system for any more fault codes. If any are present, they should also be investigated.
  3. Clear the error codes and drive the vehicle (if no serious issues are present) while an OBD scanner scans the live data.
  4. If the P0037 code persists, check all wiring for damaged or loose connections.
  5. Check the power and ground connections on the sensor.
  6. Examine the HO2S heating element for issues.

Testing the Wiring

Use a digital voltmeter to check for a 12+ volt battery supply to the heating element with the key switched to the on position but with the engine off.

If no voltage is displayed, repair any open or short circuits in the 12 volt supply, but check to see if any blown fuses are the result of the short circuit.

Disconnect the ground (control) circuit from the ECM wire connection if the battery feed is ok, then test the circuit for resistance.

If there infinite resistance is found, repair the open in the circuit.

How to Fix

Check for all possible causes of P0037 and attempt the most likely repairs, then clear the OBD system of fault codes, test drive the vehicle and scan again.

If the code reappears after you’v attempted a fix, try the next repair option.

Common fixes for a P0037 fault code are to:

  1. Reset the code after verifying it using a professional OBD reader. After that, test drive the vehicle to determine whether the issue code has been cleared or if it reappears.
  2. If the code appears, check voltage and ground, then repair or replace any loose or faulty wiring to the HO2S.
  3. If this does not fix the issue, the HO2S sensor should be replaced.
  • Andy Lewin

    Andy Lewin is a senior mechanic, ASE qualified master technician, and an experienced automotive engineer. He's passionate about serving the automotive community with the highest-quality and trustworthy information on all things automotive. He loves to write about car repairs, maintenance, car modifications and tuning, faults, and much more.

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