Low Voltage In The Oxygen O2 Sensor Circuit Fault Code P0137 (B1 S2)

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Low Voltage In The Oxygen O2 Sensor Circuit Fault Code P0137

When a sensor in the car detects that a component is malfunctioning, it will produce an error, which will set off a code and turn on the engine light.

Thanks to fault codes, it takes less time to diagnose problems when you can pinpoint the failing system. Today, we’ll discuss the error code P0137.

Low Voltage In The Oxygen O2 Sensor Circuit Fault Code P0137

It is a standard error code related to your car’s O2 sensors and emission control system.

In this manual, we will define this code, list the most typical symptoms, describe how to diagnose it, and show you how to resolve it.

What is the meaning of the P0137 error code?

O2 sensor code P0137 is used. In a nutshell, it indicates that the oxygen sensor’s voltage signal is shallow. This code corresponds to bank one on cars with two banks of cylinders (V6, V8, and some I6).

An O2 sensor is what?

The amount of oxygen leaving the engine is measured using an oxygen sensor. This data is used by the ECU (Engine Control Module) to modify the air/fuel ratio.

One or two sensors perform this measurement in your car, one before and one after the catalytic converter.

The ECU lacks a critical component without these sensors, which can impact the car’s operation and fuel efficiency.

Which direction is upstream or downstream for Bank 1 Sensor 2?

The O2 unit in Bank 1’s Sensor 2 is seen downstream. The downstream sensor is placed immediately after the catalytic converter, and the upstream one is placed close to the exhaust manifold just before it. The downstream sensor, sensor 2, is referred to as P0137.

A surefire way to find a suitable sensor is to start with the first one and work your way up. The timing cover is close to cylinder 1, located the farthest forward.

Inline 6-cylinder engines, contrary to widespread assumption, can also have two banks, with the first three cylinders referred to as Bank 1 and the second set of cylinders referred to as Bank 2.

What are the reasons behind the error code P0137?

The proper operation of your engine depends heavily on the O2 sensor.

Although sensor failure is uncommon, other related components, some of which may malfunction and result in the P0137 code being registered, include:

  • Defective O2 sensor
  • Exhaustion harm
  • Failing the catalytic converter
  • ECU issues
  • Faulty wiring harness
  • Defective O2 sensor

O2 sensors are built to endure the environment by the manufacturers, but they are subject to failure like any other automobile part that is subjected to heavy wear.

Before and after the exhaust exits the catalytic converter, both sensors function in tandem to monitor the oxygen concentration.

The ECU evaluates both voltage readings and compares them. The voltage measurement from sensor two is unreasonably low in the case of P0137.

Burnout of the heater core is a frequent defect that causes this error code. A ceramic bulb in the measurement method generates its voltage when exposed to exhaust fumes. Only when the sensor is about 600°F can this be done.

1. Damage to the exhaust

The voltage value may be lower than usual due to foreign air entering the exhaust. The code may also be brought on by exhaust gases escaping through an aperture. This contains an exhaust manifold with cracks.

Similar issues could potentially result from damage to the engine itself. A vacuum leak may cause an engine to run low.

2. Catalyst malfunction

Because catalytic converters are built to last a long time, problems with the engine typically arise before those with the catalytic converter. Unburned fuel or recurrent engine issues frequently harm the catalytic converter.

P0137 is one of the issues this causes. The cat may not be doing its function of digesting the exhaust gases in this situation, which could result in the P0137 code being set.

There is not enough oxygen in the engine, according to the O2 sensor. The PCM then modified the air-fuel mixture in response to this, making it leaner.

3. Faulty wiring harness

The most frequent cause of a P0137 error code is this. The wires can be harmed by rodents or stones, which results in voltage loss.

Additionally, the sensor connector may be damaged. The connector or the accompanying wires may melt due to the heat in which the O2 sensors operate.

4. ECU-related issues

P0137 is one of many problem codes that might result from a malfunctioning PCM. You won’t know until you’ve gone through the complete list of topics whether a single component is malfunctioning because software issues frequently cause this. ECU failures are uncommon, nevertheless.

What are the P0137 trouble code’s typical symptoms?

If we examine the numerous issues that can result in a lean air-fuel mixture, we find that most of them are caused by leaks or cracks where air can enter or exit.

Therefore, it is likely that the P0137 code’s symptoms would be connected to these typical symptoms.

  • Check-engine indicator
  • Leaks of exhaust gases
  • Power outage
  • Idle rate
  • Check-engine indicator

The check engine light is one of the earliest warnings that anything is wrong, just like any other trouble code.

The light might flash instead of just lighting up when a P0137 error code is present. This is because an incorrect air-fuel ratio might result in various catastrophic issues.

1. Leaking exhaust gas

Damage to the exhaust is one of the causes of a P0137. Therefore, the smell of exhaust from your car is one of the unmistakable indications of this issue.

The entrance of exhaust fumes into the passenger compartment may be an even more telling symptom.

2. Power loss

Engines are made to run at a particular air-to-fuel ratio. Failure of power may result from a lean air-fuel combination.

This symptom is highly common because the ECU will detect a P0137 within two minutes of a part failing and adjust the fuel trim to compensate for it.

3. Idle pace

Undoubtedly, a rich air/fuel mixture has a unique set of issues. Due to the excess fuel’s inability to ignite, stalling or poor starting behavior is likely to happen.

Always look for rough idling as a sign that the engine is struggling to find the proper combustion settings.

How to identify and address the root of error code P0137?

Any car owner will become anxious if their check engine light is flashing. Even while it may be unsettling, the best course of action is to maintain your composure and definitively diagnose your car.

The problem with a CEL, even one that is intermittent, is that it might indicate practically anything. You should first get out your dependable OBD II scanner and perform a thorough diagnostic on your vehicle.

1. OBD II Reader

When a CEL appears, a scan tool should always be your first diagnostic tool. You can connect to the vehicle’s ECU and examine all the recorded codes using an ODB II reader.

You’ll be able to determine whether the codes are recent or old and whether they are severe.

The best part is that most scanners let you view real-time data from the ECU, which can aid in making a diagnosis. Connect it to the OBD II port to begin, then start the scan.

Since it varies from car to automobile, check the owner’s manual for the precise placement of the port.

You are also able to access the real-time oxygen sensor data in addition to being able to recognize the P0137 code.

Although the gradient will be slower, the downstream sensor we are examining should exhibit prominent peaks and dips.

2. Visual examination

External factors are the most frequent causes of a P0137. Therefore, it only makes sense to check for damage in and around your car before considering more invasive diagnostic procedures.

The most excellent place to inspect your exhaust system is below an elevator, but jacking it up and checking it will do just as well.

Examine the exhaust manifold, catalytic converter, and sensor for damage. With other error codes, the cat frequently sustains internal damage.

Due to the nature of the exhaust material, a minor leak is unlikely to occur; instead, the material will either be wholly loose or the holes will be pretty broad. The same applies to manifold cracks.

3. The wiring harness has been harmed

It makes it reasonable that a circuit break might result in low voltage since the O2 sensor is one of the P0137 code’s most likely sources.

This can be caused by issues with the wire harness or the ECU. However, the latter is more common.

A common cause of P0137 is a loose or faulty connector. Examine the wiring harness and sensor connector for any exterior damage.

Melted plastic near the sensor’s tip or burn marks, such as black soot, are typical warning signs.

4. Test using a multimeter

Either an oscilloscope or a multimeter can be used to do this test. Although most car owners have a multimeter on hand, an oscilloscope will allow you to measure the voltage and wavelength of the signal.

Compared to many of the other sensors your car will encounter throughout its life, the O2 sensor has a slightly different appearance.

The harness uses a three-wire arrangement, but there are now two extra wires. These cables are the heater’s positive and negative conductors.

The top of the sensor is where the ground (brown), signal (red), and live (green) wires enter. These wires link to a different connection, which then connects to the wiring harness.

Touch the positive probe to the signal wire and the negative probe to the closest ground on your car to diagnose the sensor.

Your sensor should register between 0.2 and 0.8 volts once you have probed it. Depending on the sensor manufacturer, the numbers vary a little, but since the P0137 code is mainly for low voltage, that’s what you want to check for.

5. Vacuum leaks

Even while vacuum leaks can be caused by holes in the exhaust pipe, finding those holes can be much more complicated if the leaks come from the engine.

Your engine may run lean because of this and generate the P0137 error code.

You can determine if you have a vacuum leak with a vacuum tester. Any engine vacuum hose can be used to connect your vacuum tester.

Your gauge at idle should read between 14 and 22 HG. There is a leak if the pressure changes or drops too low.

There are numerous do-it-yourself techniques to pinpoint the location of the leak. Although using a smoke machine is the safest option, not everyone can access such tools.

The second-best option is to start the engine and then apply starter spray to the questionable vacuum lines. You’ve identified the leak if the idle returns to normal.

However, since beginning sprays can catch fire, proceed with caution and at your own risk.

Does the P0137 error code automatically go away?

Although the P0137 error code can be cleared manually, it is preferable. You’ll save a ton of time and hassle by doing this. The code should disappear if you didn’t access one after multiple drive cycles.

The issue with this is that it will take some time to see if the problem has been resolved because drive cycles often include driving the car a specific distance to a particular RPM.

With P0137, is driving possible?

Many vehicles may limit your speed or not let you drive with a P0137. Even if your car does not have limp mode, you should still avoid driving if you have an active 02 sensor issue.

If left unchecked, you may need to repair a catalytic converter or exhaust manifold, but you risk destroying your engine.

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