P0137 – How To Diagnose A Bad O2 Sensor?

by Conner Mckay

To achieve optimum performance, an internal combustion engine needs the right air/fuel ratio. The engine control module controls the air/fuel mixture ratio going into the engine. It accomplishes this through the use of automotive sensors, one of which is the oxygen sensor installed on the car. When the circuit or sensor malfunctions, the onboard diagnostic system will display the P0137 error code.

Vehicles have two oxygen sensors: one upstream (before the catalytic converter) and one downstream (the O2 sensors after the catalytic converter). Sensor 1 determines the air/fuel mixture ratio and sends the information to the ECM for modification. Sensor 2 monitors the catalytic converter.

To provide an accurate reading, every O2 sensor requires an average operating temperature. As a result, manufacturers added a heater element to these sensors, allowing them to warm up quickly.

This code can be caused by a defective oxygen sensor, although it’s not always the case. Learn how to effectively diagnose a P0137 issue code before it causes more engine harm by reading on.

P0137 Code

The diagnostic code P0137 indicates that the voltage produced by the #2 oxygen sensor, which is placed along bank 1, is lower than intended. P0131 is the code for the first oxygen sensor. For at least 20 seconds, the voltage must fall below 450 millivolts. This means that the engine’s No. 2 O2 sensor isn’t giving the ECM proper information.

Because the #2 oxygen sensor is placed downstream of a vehicle’s catalytic converter, the engine in issue is unable to discern downstream exhaust values. As a result, an engine’s management software cannot provide a precise picture of combustion efficiency on the afflicted bank.

The generic powertrain trouble code indicates a malfunction with the second oxygen sensor placed on Bank 1. The code was triggered because the voltage of the oxygen sensor had been too low for at least two minutes. The ECM is in charge of reading the voltage and programming the code.

What Is The Difference Between Bank 1 And Bank 2?

The terms “bank 1” and “bank 2” simply refer to the engine’s left and right sides, respectively. On the same side as cylinder 1, bank 1 is positioned. Cylinder 2 is located on Bank 2’s side. If the car has a transverse engine, Bank 1 is usually located at the front.

Checking your car’s maintenance manual is the simplest approach to figuring out which cylinder bank to use. You can also seek cylinder numbers on the cylinder block or head by looking for stamps. The crankshaft pulley is located in the front portion of the engine. The engine is not located on the side closest to the front.

You can’t just claim that bank 1 is on the driver’s side or vice versa because cylinder 1 can be on either side of the engine. We drive on the opposite sides of the road all around the world, so figuring out which side bank 1 or bank 2 is on is both perplexing and deceiving.

What Is The Distinction Between Sensors 1 And 2?

The sensor number identifies the location on the exhaust system of the O2 sensor or the exhaust temperature sensor. The first sensor is closest to the engine, and the last is furthest away from the exhaust system.

The usual rule when it comes to O2 sensors is:

Some diesel engines include many exhaust temperature sensors, such as sensors 1- 2- 3- 4, and so on. The first sensor is closest to the engine, while the last sensor is at the back of the exhaust system.

What Is The Function Of The Oxygen Sensor?

To detect the oxygen content of exhaust gases, an oxygen sensor is usually installed in the exhaust stream of automobiles. The sensor compares the oxygen content to the oxygen percentage in the air and sends the results to your vehicle’s Engine Control Module (ECU). Not only can a properly functioning oxygen sensor help your vehicle pass an emissions test, but it will also increase its fuel efficiency.


Multiple sensors in contemporary cars will offer the engine computer two readings and more data. Before and after the catalytic converter in the exhaust pipe, there are upstream and downstream oxygen sensors, also known as Sensor 1 and Sensor 2, respectively.

  1. The upstream O2 sensor monitors the engine’s burning efficiency and sends the data to the ECU, which determines the ideal air-fuel ratio to keep the engine running effectively and powerfully.
  2. The downstream O2 sensor readings, on the other hand, are compared to the upstream O2 sensor readings. When the measurements are close enough, the car computer will create a catalytic converter diagnostic trouble code, indicating that it is not functioning properly and preventing harmful particles from entering the air.

What Are The Signs And Symptoms Of P0137?

The failure of most automotive system components sends some warning indicators to the driver before they entirely halt, and bank 1 sensor 2 is no exception.

The P0137 error code has the following symptoms:

  • Emissions are poor
  • The fuel economy is poor
  • The Check Engine Light is on
  • Engine performance has been reduced
  • Failsafe Mode
  • Rough Idling
  • Low Voltage
  • Engine Stuttering

What Causes A P0137 Code

P0137 is a generic fault code, which means it can appear on a wide range of vehicles. The interpretation of this code, however, may differ from one brand to the next. For example, P0137 on a Toyota signifies “Oxygen Sensor Circuit Low Voltage Bank 1, Sensor 2,” whereas P0137 on a Chevy means “Heated Oxygen Sensor (HO2S) Circuit Low Voltage Bank 1, Sensor 2.”

Because translations change, the likely causes may also differ depending on your vehicle’s make and model. The most prevalent reasons for an O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2) problem, often known as code P0137, are as follows:

  • Malfunctioning ECM sensor heating
  • Bank failure 1 oxygen sensor 2 heater
  • A lack of grounding
  • The control circuit has been shortened
  • A fuse has blown
  • A split in the wire connecting ECM and H02S2
  • At the back sensor of the catalytic converter, there could be an escape leak
  • The catalyst may become clogged
  • There is a problem with the motor
  • The fuel pressure is either too high or too low

P0137 Code Solutions

Check the following components to fix the DTC code P0137:

  • Replace the sensor that has failed.
  • If an exhaust leak is identified, it must be fixed as soon as possible.
  • Check the catalyst for clogs and clean them if necessary (to learn more, check out our guide on what does the catalytic converter do). If the failure persists, fix things.
  • Repair any open or high resistances in the O2 signal circuit.

Is Code P0137 A Serious Threat?

P0137 isn’t a serious problem that will leave you stranded on the road. That isn’t to say you shouldn’t try to remedy it. It’s a minor concern if a check engine light or service engine light illuminates for a short period of time and then disappears. If the check light comes on while the engine is running due to an error code, it signifies there is a problem that has to be fixed.


If you ignore the error code for a long time, it will result in system problems such as high fuel consumption and poor emissions. It may cause the car to enter failsafe mode, resulting in engine stuttering, rough idling, and poor engine power.

Common Diagnostic Errors With Code P0137

Examine the sensor wiring before replacing the 02 sensors. The most typical cause of P0137 is bank 1 sensor 2 wiring, not the sensor itself. The fault code hasn’t been reset. Prior to repairing, always try to reset the fault code. The code may be wiped out after resetting the code with the OBD2 scanner.

Following the measures mentioned below will help you avoid misdiagnoses:

  • Make sure the exhaust leaks are addressed before the sensor to avoid excess oxygen entering the exhaust stream and causing low voltage readings.
  • Oil or coolant contaminants that could foul the oxygen sensor should be thoroughly inspected.
  • To minimize unreliable sensor readings, the broken harness should be correctly rebuilt.
  • If the oxygen sensor has been removed, inspect for damage from a damaged catalyst, and replace the catalyst if it has fallen apart (to learn more, check out our guide on what’s in catalytic converters and what are catalytic converters, as well as what is a catalytic converter made of).
  • To prevent extra oxygen from entering the exhaust stream and creating low voltage readings, seal any exhaust leaks before the sensor.
  • Check for contaminants in the O2 sensor, such as oil or coolant, that could cause it to fail.
  • To avoid unpredictable sensor readings, repair any harness that is damaged appropriately.

Examine the removed O2 sensor for damage caused by a faulty catalyst, and replace it if necessary.

Is Driving With A Defective Oxygen Sensor Safe?

Yes, if your engine starts and you have little difficulty driving, you can drive with a faulty oxygen sensor. However, don’t leave it alone for more than a few days because it could cause safety issues and cause other parts of your vehicle to malfunction.

A faulty oxygen sensor can result in sluggish and rough driving, as well as stalls, poor fuel efficiency, and high emissions. And if you leave it there for an extended period of time, it might cause serious issues with the engine and catalytic converter, which could cost thousands of dollars to repair or replace.

As a result, you should get the oxygen sensor examined as soon as possible, perhaps by visiting a mechanic on the weekend. You may scan the OBD2 code, check possible causes online, and try a few basic fixes if you have your own car diagnostic equipment.

Cleaning the O2 sensor or replacing a pipe linked can sometimes clear a fault code indicating that the O2 sensor is malfunctioning. Unfortunately, there is no temporary fix for bad O2 sensors once they have worn out. You may either have it installed by a reputable mechanic or you can buy it and install it yourself.

How Much Does It Cost To Fix Code P0137?

P0137 can be caused by a faulty O2 sensor, bad wiring, or exhaust leaks, among other things. It’s impossible to give an accurate estimate without first examining the problem thoroughly. Most shops will give you an hour of “diag time” when you bring your car in for service (the time spent in labor diagnosing your specific issue).

This can cost anywhere from $75 to $150, depending on the shop’s labor rate. If you have the shop execute the repairs for you, many, if not all, of the businesses will apply the diagnostic cost to any required repairs.

Following that, a company will be able to give you an accurate repair quote for your P0137 code.

P0137 Repair Costs Estimated

One or more of the following repairs may be required to resolve the underlying issue for error number P0137. The cost of the needed parts as well as the cost of labor required to accomplish the repair are included in the estimated cost of repair for each potential repair.

  • Sensors for oxygen are priced between $200 and $300.
  • Repairing an exhaust system costs between $100 and $200 (if welded to repair).
  • $1300-$1700 for a fuel pump.
  • A fuel pressure regulator costs between $200 and $400.
  • The cost of repairing a vacuum leak ranges from $100 to $200.

Methods For Diagnosing Code P0137

Engine code P0137 can be triggered by a defective oxygen sensor, improper wiring, or an exhaust leak, among other things. Follow the steps below for an accurate diagnosis if you want to make a low-voltage O2 sensor fix at home without spending money on parts.

Diagnosis requires more advanced equipment than the OBD tool can provide, and it can be a lengthy and labor-intensive process for inexperienced DIYers.

Tools Required:

  • Fuel Pressure Gauge
  • Multimeter
  • Water Spray Bottle

Step 1: Inspect The Wiring Of The O2 Sensor

Visually inspect the O2 sensor wire and harness connectors for any signs of corrosion or physical damage. As needed, make repairs.

Step 2: Inspect The Exhaust System For Leaks

Examine the engine and the O2 sensor for any exhaust leaks. This includes the exhaust manifold or headers, flex pipes, the area around the turbocharger, and if your car has one, the catalytic converter (s). Make repairs as needed.

Step 3: With The OBD Sensor, Check The Voltage Of The O2 Sensor

Warm up the engine of your automobile. Examine your O2 sensor’s voltage (bank 1, sensor 2).

It should be in the range of 0.1-0.95 volts. You’re probably dealing with a malfunctioning O2 sensor if it’s less than this. To be sure, keep diagnosing.

Step 4: Examine The Fuel Pressure

With a fuel pressure gauge, check the fuel pressure and compare it to the manufacturer’s specifications for your car. As described in step 3, low fuel pressure can cause the engine to run lean, resulting in low voltage readings from the O2 sensor. In this instance, the sensor is accurate, and the lean running condition must be addressed.

Step 5: Check For Vacuum Leaks In The Region

Check the vacuum lines and any intake connections for signs of disconnection or outside air leakage with a visual and aural inspection. This includes the intake pipe that runs from the throttle body to the mass air flow sensor.

There could be a vacuum leak if you hear a hissing sound emanating from these pipes. As you spray water over the intake region, pay attention. There is almost certainly an intake leak if the engine stutters and runs rough for a few seconds before recovering. Concentrate the water stream on different hoses and gaskets until you find the leak.

Advice On How To Avoid P0137 In The Future

Vacuum leaks and faulty wiring can cause a variety of catastrophic engine issues. An anti-corrosion coating applied to your engine can aid in the preservation of these components. You can also be proactive when it comes to spotting problems. Check the wires and hoses on a regular basis to make sure they’re well-connected and far enough away from engine components to avoid harm.


  • To remove the restriction, replace the catalytic converter.
  • Restore the O2 signal circuit’s electrical short.

How To Fix P0137 Code

1. Oxygen Sensor

The oxygen sensor is a critical automobile component that should never be overlooked. It’s possible that there’s a problem with it, causing the P0137 code to flash.

2. Is Your Mass Air Flow Sensor Broken Or Damaged?

Don’t worry, we’ve got answers to all of your troubles.

3. Absolute Pressure Sensor In Manifold

A P0137 code can be caused by the Manifold Absolute Pressure sensor. So, to avoid any additional troubles, be sure to replace it online.

Mechanics Suggestions For The P0137 Code

If the P0137 DTC is related to any other codes, you should fix them first. The P0137 code can be caused by a variety of issues, so you might be able to remedy this one by addressing another. For example, the O2 sensors include a built-in heater to maintain them above 600 degrees Fahrenheit.

The O2 sensor may throw this signal if the internal heater resistance becomes too high. You should start with the DTCs for the O2 sensor heater. You can only be sure you’re dealing with an oxygen sensor problem if you eliminate all other engine codes first.

How To Fix P0137 Code?

The following are some solutions to the O2 sensor low voltage fix. However, make sure you have a good diagnosis before altering any parts. Otherwise, you could be squandering your money.

1. Replace the O2 Sensor that Isn’t Working.
2. Fix the Exhaust Leak
3. Exhaust Parts

The oxygen sensor is working properly, yet the OBD code P0137 continues to appear? Then there must be some exhaust-related faults. Replace them as soon as possible.

4. Is the P0137 Code Flashing on your Powertrain Control Module?

A mechanic should look over your Powertrain Control Module.

5. Engine Control Unit

Every vehicle’s Engine Control Module is a vital component. If you take care of it, you may rely on us to buy high-quality Engine Control Modules online.

6. Fuel Pump

The fuel pump may be malfunctioning, resulting in the P0137 code being shown repeatedly. If you don’t replace it, you can have some serious problems.

Rationality Checks Are Performed By ECM/PCM

Both the upstream and downstream sensors have an inbuilt heater since O2 sensors must operate at temperatures above 600°F. The O2 sensor may generate this code if the internal heater’s resistance is too high, so make sure you first consider the O2 sensor low voltage fix.

A traditional O2 sensor’s voltage range can be anywhere from 0 to 1 volt (0 to 1000 mV), but it’s commonly between 200 and 900 mV. The upstream sensor moves from above to below. When everything is working properly, the downstream sensor should be at 5 volts; it is evaluating the catalytic converter’s ability to hold oxygen; thus, it should move slowly, usually staying above. The voltage is 5 volts.

The P0137 is saved if the downstream sensor falls below a certain threshold and stays below that threshold for a defined period of time while the upstream O2 sensor remains within acceptable limits. The ECM/PCM uses “rationality checks” to discover faults with sensors that should be working in a specific manner.

How To Test O2 Sensor With Scanner

Connect the OBD2 scan tool to the diagnostic link on your vehicle (DLC). The DLC is almost triangle-shaped and includes 16 pins.

Start your car so the scanner can connect to the vehicle’s onboard computer. Make sure you don’t start the car’s engine; instead, turn the key in the ignition. Reattach the scanner or give it a slight shake if it stays blank after this.

After the scanner has started, select ‘Trouble Codes’ or ‘Codes’ from the menu.

Choose the system you want to troubleshoot from the drop-down menu. Two or more codes will display on your screen as a result of this procedure. It’s possible that the codes that appear are either Pending or Active codes. The types of codes listed above are the most common. There are, however, additional types of codes.

The Check Engine Light is kept on by active codes, also known as live codes. They suggest that the system has a flaw that must be addressed. Pending codes indicate a potential problem. It indicates that an emission control system has failed previously, and if it fails again, the Check Engine Light will illuminate. When it is activated, the pending code becomes an active code.

Decipher the code. The OBD2 scan tool will identify the problem and assign a code to it. You can look these codes up on the internet if you don’t know what they mean.

P0137 Code Facts:

  1. P0137 is the OBD-II generic code that indicates the O2 sensor for bank 1 sensor 2 is failing to increase the voltage output above .21 volts, indicating excessive oxygen in the exhaust.
  2. The ECM detects the low voltage problem and turns on the Check Engine Light.
  3. The P0137 code occurs when the ECM sees the voltage of the O2 sensor for bank 1 sensor 2 below .21 volts when the ECM has commanded the fuel to a targeted rich condition on that bank of the engine.
  4. Exhaust leaks can cause the voltage output from the O2 sensor to be low.
  5. Symptoms of the P0137 code include the engine running rich during the testing of the sensor for problems, the Check Engine Light being illuminated, and exhaust leaks before or near the O2 sensor in question.
  6. To diagnose the P0137 code, a mechanic scans codes and documents freeze frame data, then clears codes to verify failure, monitors O2 sensor data, checks the O2 sensor wiring and the harness connections, checks the O2 sensor for any physical damage or fluid contamination, and follows the manufacturer’s specific pinpoint tests for further diagnosis.
  7. Common mistakes when diagnosing the P0137 code include not repairing any exhaust leaks before the sensor, not checking the O2 sensor for oil or coolant contaminants that could foul the sensor, not repairing any damaged harness properly to prevent erratic readings from the sensors, and not checking the removed O2 sensor for damage from a broken catalyst.
  8. The P0137 code can lead to poor fuel mileage and possible premature failure for some engine components if not repaired.
  9. Repairs that can fix the P0137 code include replacing the O2 sensor for bank 1 sensor 2, repairing or replacing the wiring or connection to the O2 sensor for bank 1 sensor 2, and repairing exhaust leaks before the sensor.
  10. The O2 sensor circuit for bank 1 sensor 2 is used to give a voltage feedback to the ECM showing how much oxygen is in the exhaust stream to help the engine control the fuel-to-air ratio better. The low voltage condition is excessive oxygen in the exhaust or problems causing the issue.


What Are The Symptoms Of P0137

P0137 is a generic OBDII code. It, therefore, applies to all types of vehicles. Typically, the service engine light is the only symptom of P0137. Other symptoms may also be present, like if the engine is in a bad state of repair. You might also notice that the exhaust smells bad and the service light is on. Besides that, your MPG will also be low. Most of the time, it isn’t a risk of a breakdown. Anything that causes the service engine light to appear, on the other hand, should be dealt with as quickly as possible.

Where Is The Bank 1 Oxygen Sensor

It’s simple to identify bank 1 sensor 1 on a four-cylinder engine. Simply open the hood and look on the exhaust manifold for the catalytic converter. It may be hot, so be careful not to touch it. Sensor 1 of Bank 1 is placed directly in front of the catalytic converter. Because six, eight, ten, or twelve-cylinder engines often have two upstream sensors, determining which one is bank 1 sensor 1 can be difficult. The passenger side of the engine is commonly designated as Bank 1 and the driving side as Bank 2, as is the case in most European automobiles.

Can I Drive With A P0137

For a brief period of time, driving with trouble code P0137 is permissible. If a lean air/fuel ratio causes this code, driving with it for an extended period of time could cause more engine damage.

Enlist The Causes Of P0137 Chevy

A variety of factors can cause code P0137. This can include an oxygen sensor failure (most common), or that the O2 circuit has a voltage short. Otherwise, it could be caused by leaks in the exhaust or low fuel pressure. If not, it could also be that the engine is operating lean.

What Is The Cost To Diagnose The P0137

The P0137 code requires 1.0 hours of labor to diagnose. The time it takes to diagnose a car and the labor costs vary by region, vehicle make and model, and even engine type. The average hourly rate in an auto repair shop is $75 to $150.

Final Verdict – P0137

The diagnostic trouble code (DTC) P0137 stands for “O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2).” This can occur for a variety of reasons, and a technician will need to determine what triggered the code in your circumstance. OBD-II codes assist you in determining what is wrong with your vehicle. According to your diagnostic tool, a P0137 error number means there’s a problem with one of your vehicle’s oxygen sensors.

This article will show you what a P0137 is, what causes a P0137 code, and how to diagnose and fix it. The sensor is not generally to blame. Check for other possible causes and make sure they’re operating before replacing the O2 sensors. The heated oxygen sensor can be repaired; however, the procedure is nearly identical to replacing it. However, rather than repairing the sensor, it is preferable to replace it.

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