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P0037 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.

Definition

The circuit is low on heated oxygen sensor (HO2S) 2, bank 1, heater control.

Meaning

OBD II fault code P0037 is defined as “Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2). It is set when the PCM (Powertrain Control Module) detects a signal voltage from oxygen sensor #2 that does not fall within the predefined range for that sensor. Note that “Bank 1” refers to the bank of cylinders that contains cylinder #1, and that “Sensor 2” refers to the oxygen sensor that is located after (downstream of) the catalytic converter(s).

Causes

A cause behind this trouble code could be burnt wiring. Wiring that runs too close to hot exhaust components can become burnt over time. Short circuits caused by burnt wiring could also be the problem.

Another reason for this code could bad connections caused by corrosion, or impact damage caused by road debris. Bad ground connections, low battery voltage or blown fuses (where applicable) on the heater control circuit could also be the cause.

Symptoms

The symptoms of this problem are pretty straight forward. Rich-running condition, lean-running condition, an increased fuel consumption, loss of power and rough idling are a few of the symptoms. If there is visible black smoke from the tail pipe, it is hard to start the car, the check engine light is on or there are stored trouble codes, these could be symptoms as well.

Diagnosis

Check to see if there are any other codes along with P0037 and clear your Check Engine Light with FIXD. Visually inspect the wiring around the bank 1 HO2S2 for disconnection or damage.

If the wiring directly attached to the HO2S sensor is damaged, replace the HO2S2.

Check resistance of the heater element to ensure it is within the specified range. If out of spec, replace HO2S2.

Check voltage to the O2 heater. If no voltage is detected (open circuit), check for a blown fuse or break in the wire.

Check ground to the heater, if no or poor ground, check for loose ground, clean, and tighten.

If the problem persists, consider replacing the HO2S sensor, before replacing the ECM.

Common mistakes

Prematurely replacing the HO2S2 (heated oxygen) sensor without visually inspecting the wiring of the control circuit for disconnection or damage.

How serious is this?

This trouble code will not prevent your vehicle from operating, but it will cause it to fail emissions tests. The most common error(s) include lowered fuel economy, rough engine performance, and HO2S2 sensor errors. It is recommended to have this code fixed to prevent further damage to the vehicle. Do not wait to have this code fixed, as this could lead to severe damage.

What repairs can fix the code?

Have a certified technician verify the code with a scanner. Reset the fault codes and perform a road test.

If the P0037 code returns then follow the test procedure. It can have several problems, but wiring being damaged by excessive heat from the exhaust is most common one. Make certain the wiring is good and has proper voltage and ground to the sensor before replacing the sensor. 

Test Procedure

With the key on and the engine off, use a voltmeter to check for 12+ volts fused battery feed to the heater element. If there is no voltage present, repair the open or short in the 12-volt feed circuit by first determining if it is necessary to replace any fuse blown from the short. If the battery feed is intact, remove the ground (control) circuit from the ECM wiring connector and check for resistance on the circuit. If there is infinite resistance, repair the open in the circuit. If the control circuit checks out, suspect a bad O2 sensor. Replace and re-check.

Having experienced this problem in the past, the most common problem is damage to the sensor wiring, either from improper installation or the wiring clamps failing causing the wires to touch the exhaust system, including the catalytic converter which is the hottest part of the exhaust. The rear sensor is most likely to be removed or exposed to physical damage during work on the exhaust or driveline which creates many potential problems. If the wiring on the sensor itself is damaged, do not try to repair it as it most likely will not work properly. In these cases, just replace the sensor.

Related codes

P0038 relates to “Oxygen Sensor Heater Control Circuit High (Bank 1 Sensor 2).”

Conclusion

The P0037 code is not something that can be ignored. If left untreated, it can cause serious damage to the vehicle’s engine. You should get it looked at by a professional if symptoms prolong and the repairs do not work.

Fortunately, there is an effective process to determine what the cause of this code is, and the solutions are clearly defined. In most cases, the repairs will work and the problem will be solved.