P0037 Code: Meaning, Symptoms, Causes, Diagnostics, And Fixes

Error code P0037 is commonly defined as Heated Oxygen Sensor Heater Circuit (HO2S) low, Bank 1, Sensor 2. In simpler terms, it means that the heater element circuit of the HO2S has a problem. P0037 code is triggered when very low voltage through the heated oxygen sensor heater circuit is detected by the Engine Control Module.

 When the P0037 code is triggered, you should check the oxygen sensor.
When the P0037 code is triggered, you should check the oxygen sensor.

P0037 Code Definition

  • P0037 Generic: HO2S Heater Control Circuit Low Bank 1, Sensor 2
  • P0037 Toyota: Oxygen Sensor Heater (Rear) Open
  • P0037 Nissan: Heated oxygen sensor (HO2S) 2 Bank 1 – heater voltage low
  • P0037 Subaru: HO2S Heater Control Circuit Low – (Bank1 Sensor2)
  • P0037 Mazda: HO2S) Heater Control Circuit Low (Bank 1, Sensor 2)

What Does P0037 Mean?

Code P0037 means that the ECM has detected low voltage from the Oxygen sensor. The low voltage is caused by oxygen content in the exhaust being outside the set values. The engine may not be running correctly. The ECM will try to adjust the fuel and air ratio to correct this code by regulating the amount of fuel delivered to the engine. The sensor helps control emissions when the engine is running.

When the PCM detects any readings from the heated sensor outside of the allowable range, the P0037 error appears. Some vehicle models have more than one heated oxygen sensor. In this case, each sensor has its own circuit to control its heating. P0037 error code can also appear if the PCM detects an open circuit.

What Are The Symptoms Of The P0037 Code?

  • Check engine light on
  • Service engine soon warning light
  • Failsafe mode
  • Low power
  • Rough idling
  • Engine hesitation
  • Abrupt shifting patterns in automatic transmissions
  • Lower fuel economy
  • Reduced engine performance

What Are The Causes Of P0037?

There are several possible causes of P00037 code:

  1. One of the most common causes is a faulty Bank 1 Oxygen Sensor 2. The sensor fails to send the correct data to the PCM. It occurs if the sensor is damaged or defective. It can also mean the sensor has a poor grounding or has a shorted Control Circuit.
  2. Another major cause of P0037 is burnt wiring. Wiring running very close to the exhaust will burn out and cause a short circuit or an open circuit. The exhaust system is usually very hot, especially at the end of the catalytic converter where the sensor is located. Blown fuses on the heater control circuit can also cause this code.
  3. When there is a malfunctioning ECM Sensor Heater driver, the code can be set.  Failed battery input connector may lead to this problem.

How Serious Is P0037 Code?

The P0027 code is not a very serious issue. However, it needs to be checked as soon as possible. You can drive your vehicle with this code. If the check engine light comes up immediately after the start, the error will clear. If the check engine comes up while in operation due to the sensor error, it means there is a problem that needs to be checked. Failure to have the error resolved can lead to problems. It can affect fuel consumption, lead to poor operation, and may even damage other parts.

How To Diagnose And Fix The Code P0037?

Tools You’ll Need

  • OBD2 scanner
  • Digital multimeter

How To Diagnose The Code

To diagnose code P0037, you’ll need an OBD2 scanner that reads the code from the OBD-II system. You’ll then reset the error codes.  A test drive will be necessary to determine if the code has cleared or returns. If the code is still present, then you have to fix it.

How To Fix The Code

  1. Using the OBD2 scanner, check the code and any other code that may be present. You should do this with the key on and the engine turned off.
  2. After confirming the P0037 code, you should first carry out a visual inspection and check for blown fuses, burnt wiring, damaged wiring, and broken connectors. If you notice any damage, replace and rescan to check if the code has gone.
  3. Next, use a digital multimeter to check the battery to the heater element. It should read 12 volts, if no voltage, repair the open/short circuit in the 12v feed.
  4. Besides voltage, you should also check resistance to the heater element. The resistance should be around 8 Ohms. If the resistance is more or less than this by more than 10% then the P0037 code will be activated.
  5. Check the grounding to see if any loose, tight, or poor grounding should be fixed. While at it, clean the grounding off any debris. Ground affects the heated sensor, so if the grounding is damaged it won’t work properly.
  6. After you have taken these steps and the code still persists, the oxygen sensor itself is the problem. Replace it and recheck the code.

The sensor is not usually a problem when you experience a P0037 code. Replace the sensor after you have checked all other possible causes. The heated oxygen sensor can be repaired but the cost of repair and the cost of buying a new one is almost similar. It is advisable to go for a new one.

Common Mistakes While Diagnosing Code P0037

Always start checking the wiring. In most cases, this is the problem rather than the sensor. The heat of the exhaust may cause problems with the wiring.

Another common mistake that many people, including mechanics, is to start repairs before attempting to reset the fault. At times, the error is caused by sensor problems that will clear after a reset.

Tips To Avoid P0037 In The Future

Rerouting wiring away from the hot exhaust will avoid P0037 code in the future. Burnt out wiring is the most common cause of P0037, rerouting the wiring will save this problem.

All exhaust leaks should be promptly repaired as they can lead to wrong sensor readings.

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