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For an engine to run efficiently, it must achieve the proper air-to-fuel ratio. The powertrain control module (PCM) determines how much fuel gets injected into the engine. It calculates the correct levels with the help of the sensors installed around the engine. One of the most important sensors for its operation is the oxygen (O2) sensor.

There is one oxygen sensor before the catalytic converter (referred to as sensor 1) and another located after the catalytic converter (referred to as sensor 2). The PCM uses the signal from sensor 1 when calculating fuel delivery. On the other hand, the module primarily uses the signal from sensor 2 when determining the status of the catalytic converter.

Each oxygen sensor must warm up to work properly and relay accurate information. Inside the sensor is a heater wire that helps it come up to its working temperature quicker. When the PCM detects a problem with the heater control circuit of the rear oxygen sensor, on-board diagnostics will log a P0037 code.

oxygen sensor automotive image
Code P0037 refers to a malfunction in the heating element of the downstream oxygen sensor behind the catalytic converter.

What Does the P0037 Code Mean?

Diagnostic Trouble Code (DTC) P0037 stands for “Heated Oxygen Sensor (HO2S) Heater Control Circuit Low (Bank 1, Sensor 2).” It refers to a malfunction in the heating element of the downstream oxygen sensor behind the catalytic converter.

While it is generic to vehicles from different auto manufacturers, the steps for diagnosis and repair for a code P0037 for a Nissan may vary from that of a Ford.

If you’re trying to figure out where Bank 1 is, read our guide here. To understand why oxygen sensors need to be heated, you can read our technical explanation here. Otherwise, you can proceed to the next section to quickly learn the possible causes of code P0037.

What are the Possible Causes of the P0037 Code?

  • Defective oxygen sensor
  • Malfunctioning PCM heater circuit
  • Heater control circuit issues, such as damaged wiring and poor connections

What are the Common Symptoms of the P0037 Code?

A malfunction in the oxygen sensor heater control circuit will not prevent your vehicle from operating. However, you may experience the following symptoms.

Take note that if the check engine light is on, your car will automatically fail an emissions test.

car emission test
You will fail an emissions test if your check engine light is on.

How to Diagnose the P0037 Code

A problem with your downstream oxygen sensor typically triggers the P0037 code. However, diagnosing this issue might be tricky. If you’re not very confident with your automotive DIY skills, you might be better off leaving the diagnosis to a mechanic.

Of course, you can still do the troubleshooting yourself, but you should watch the video below to find out what the process might involve.

How to Fix the P0037 Code

Fixing the P0037 code is not as straightforward as you might think since there are several possible reasons that could have triggered it in the first place. This is why having a professional mechanic do the job is a good idea.

However, you can still do the fixing yourself if you have the necessary automotive DIY skills. You may need the help of online auto repair resources and guides to figure out the appropriate fix for your car. You can also get an ALLDATA single-vehicle subscription, which should help you with this fix and other future fixes you may need to do on your car.

Just remember to consult your owner’s manual before working on your car.

Products Mentioned in this Guide

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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