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P0037 Fault Code (Causes & Fixes) HO2S Heater Control Circuit Low (Bank 1, Sensor 2)

Updated: Feb 4

✔ This article has been fact checked.

When the Engine Control Module (ECM) detects a signal voltage from oxygen sensor 2 that is not within the specified range, the "HO2S Heater Control Circuit Low (Bank 1, Sensor 2)" OBD code P0037 is generated.

If a DTC is associated to the powertrain, an OBD scanner will read it as starting with P, thus the letter "P". Generic fault codes are those of the format P0xxx.

Table of Contents:

The Meaning of a P0037 Fault Code

The P0037 error code means 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 run effectively, the engine should have a perfect air-fuel ratio of 14.7 to 1, and the HO2S (oxygen sensor) analyses the oxygen content from the exhaust to ensure this air-fuel ratio is met.

It's heated to ensure the PCM responds quickly to the closed-loop system, minimising emissions at startup.

The fault code P0037 appears when there is a problem with the HO2S heating element, in this case a too low voltage.

Is It Serious?

This diagnostic code is considered minor-to-moderate. Because the HO2S is such a minimal role in how a vehicle functions, there are usually relatively few driveability symptoms.

As a consequence, the vehicle may be driven, but it should be taken in for diagnostic and repair as soon as possible to prevent future problems such as the ones listed below.

  • poor performance

  • lower fuel efficiency

  • sensor loop failure

  • damage to other components

Signs & Symptoms

Unlike in many cases when OBD fault codes are triggered, the P0037 does not have many signs and symptoms linked with the issue. There might be a few significant indications you could notice.

You may notice the following signs:

  • Check engine light (CEL) illumination

  • Poor performance and drivability

  • Lower fuel efficiency

Possible Causes

There are several potential causes for the P0037 error code, but the following are the most common.

  • Engine bank HO2S sensor failure 2

  • Exhaust ground connection that is corroded

  • Faulty PCM sensors

  • Faulty wiring to the oxygen sensor (HO2S)

  • Water penetration causing the HO2S fuse to fail

Diagnosing the P0037 Trouble Code

Diagnosing this fault code is best done using a professional OBD scanner or by completing a diagnostic check with a skilled technician.

Many vehicles with over 80,000-100,000 miles have sensor faults that arise during start-up or sustained driving.

  1. Check to see if there are any technical service bulletins available for your vehicle's model and make sure to see if there is a known problem with your vehicle that may help you in resolving the issue.

  2. Scan your system for any more OBD fault codes. If any of these are present, they should be investigated also.

  3. Clear the error codes, then drive the car while an OBD scanner reads the live data.

  4. If the problem persists, visually inspect the wiring for damaged or loose connections.

  5. Examine the sensor's power and ground connections.

  6. Inspect the HO2S heating element.

Testing the Wiring

Check for a fused battery supply to the heating element of 12+ volts using a digital voltmeter with the key on and the engine off. If no voltage is available, repair any open or short circuits in the 12 volt supply, but first check to see if any blown fuses are the result of the short.

Disconnect the ground (control) circuit from the ECM wire connection if the battery feed is ok, then test the circuit for resistance. If there is infinite resistance, repair the open in the circuit.

Possible Fixes for a P0037 Code

It is advised that you test drive the car after each fix to determine whether the fault code is resolved. If the code reappears, try the next repair option.

Common fixes for a P0037 error code you should try are to:

  1. Reset the trouble code after verifying the code using a professional OBD reader. After that, do a test drive to determine whether the issue code has been cleared.

  2. If the code appears, check voltage and ground and repair or replace any loose or faulty wiring to the HO2S.

  3. If this does not fix the problem, the HO2S should be replaced.


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