Bank 1 Sensor 2 – What Does It Mean?

When you’re using a scanner to diagnose the problem with your car’s engine, it is essential to be familiar with the terms and fault codes on it. For example, what does Bank 1 Sensor 2 mean?

Bank 1 sensor 2 is the second of two oxygen sensors on the exhaust pipe. It is located behind the catalytic converter and measures the composition of exhaust fumes.

Read on to know more about “bank 1 sensor 2” and what it means. 

Bank 1 Sensor 2 – What Does It Mean?

bank 1 sensor 2

The second of two oxygen sensors is the Bank 1 Sensor 2, and you can find it on the exhaust pipe. It is located behind the catalytic converter and measures the composition of exhaust fumes.

V6 and V8 engines are equipped with two engine banks and two catalytic converters, with one converter for each bank. The bank containing cylinder 1 is Bank 1. Sensor 2 refers to the oxygen sensor found downstream in the exhaust behind the catalytic converter.

Bank 1 Sensor 1 Location – Upstream or Downstream?

What Is an Engine Bank?

Most Car Engines Come in Two Different Configurations

If you look at most car engines today, you will notice that they come in two different configurations. All cylinders are arranged on in-line engines, with one cylinder head and components for intake and exhaust.

Four Cylinder Units

While the number of pistons ranges from 4 to 12, the most common are four-cylinder units. The advantage of the in-line engine configuration is that it has fewer potential failure points due to having fewer parts.

Engines With V-shaped Configuration

More powerful cars, however, usually have engines that utilize a V-shaped configuration. They feature cylinders ranging in number from 6 to 12. This configuration has 2-cylinder heads, one for each engine side, with separate intake and exhaust components.

Although this makes it more compact, the additional complexity makes maintenance more difficult and costly.

Engine Sides or Banks

Car manufacturers generally refer to engine sides as banks, which are each given a corresponding number. In most in-line variants, the entire engine is considered as one bank. For engines with the more complicated V-configuration, one side is designated as bank 1, and bank 2 is the other side. 

Refer to Service Manuals for Engine Bank Names

While most car manufacturers apply similar logic in naming their engine banks, this is not universal. Make sure that you have the correct information about your car to avoid mistakes and unnecessary repairs. You may also refer to service manuals, authorized car dealers, or reputable online pages.

Look for the Markings on Ignition Cables

You could also look at the markings on ignition cables or valve covers to verify the cylinder pattern. The first cylinder, labeled as number 1, will be found on bank 1. Whereas cylinder number 2 will be located in bank 2.

What Are Oxygen Sensors?

Most modern 4-cylinder engines employ a setup with two oxygen sensors to increase their efficiency and help them conform to emission standards:

Oxygen Sensor 1

The first, which we call sensor 1, is situated between the engine and the catalytic converter. It is responsible for measuring the composition of raw exhaust gases. This data is then used by the electronic control unit (ECU) to adjust the air-fuel mixture. Should this sensor fail, it would significantly impact the engine’s overall performance and operation.

Oxygen Sensor 2

The second sensor, called the downstream sensor or sensor 2, is located behind the catalytic converter. It also measures exhaust fume composition, but the ECU uses this data to determine if the catalytic converter operates properly. Theoretically, the failure of this sensor should have no noticeable effect on engine performance.

Oxygen Sensor Testing

The majority of modern engines, however, feature a specific testing interval. At which time, they run lean or rich for a short period. During the procedure, the reactions of the oxygen sensors and the catalytic converters are monitored to assess their condition.

Sensors can yield false or implausible readings. In which case, it may cause hesitation or rough running when speeding up.

How Do Oxygen Sensors Work?

bank 1 sensor 2 code

Probe With Special Sensing Element Within

Despite their different locations and tasks, all oxygen sensors function under the same simple principle. Each sensor’s core is a probe with a special sensing element within it. As the exhaust fumes pass by, the difference in oxygen levels between the probe and the outside air creates a particular voltage. 

Values Range from Close to Zero to Almost 1 Volt

Depending on the driving conditions, the values range from close to zero to almost 1 volt. Once the engine and the catalytic converter are warmed up to running temperatures, the downstream sensors should show about 0.45 volts.

Check the Values Using a Diagnostic Tool

These values can be checked using a diagnostic tool with a live data feature or a multimeter. Modern oxygen sensors mostly contain a heating element to help achieve running conditions quicker.

What Causes Oxygen Sensors to Fail?

1. Buildup of Dirt and Soot on Probe

One of the most common reasons for oxygen sensor failure is the buildup of dirt and soot on the probe. This prevents the probe from producing accurate readings. Cleaning off the buildup would only solve the problem temporarily. It is best to replace the sensor entirely as it is the only permanent solution.

2. Heater Burning Out

Another possible cause is the heater burning out, causing a corresponding fuse to blow out.

3. Other Common Sensor Issues

Common sensor issues such as damaged wiring and loose or corroded connectors are other potential factors. 

Again, what does Bank 1 Sensor 2 mean? Bank 1 Sensor 2 refers to the oxygen sensor you can find in the exhaust behind the catalytic converter. The engines V6 and V8 have two banks and catalytic converters. Then, the bank containing cylinder number one refers to Bank 1.

Where Is the Bank 1 Sensor 2 Located

The difference between sensors 1 and 2 is their location. While both are found behind the catalytic converter, they are located on opposite sides of the engine and exhaust.

Sensors 1 and 2 Location

Sensor 1 is seen from the top of the engine and mounted before the catalytic converter. Whereas sensor 2 is mounted after the catalytic converter. In most cars, bank 1 sensor 2 can be accessed from below the vehicle.

All Oxygen Sensors Follow the Same Naming Pattern

All oxygen sensors follow the same naming pattern regardless of the bank. Sensor 1, located between the engine and catalytic converter, is the upstream sensor. Sensor 2, located after the catalytic converter, is the downstream sensor.

On a V6 or V8 engine with two catalytic converters, the bank 1 sensor 2 location is usually on the passenger side, after the catalytic converter. If cylinder 1 is located on the driver’s side, bank 1 sensor 2 will likewise be on that side after the catalytic converter as usual.

Where Is the Bank 1 Sensor 2 Fuse Located

In most vehicles, the fuse can be found inside the relay box within the bay area of the engine.

What Is the Bank 1 Sensor 2 Voltage?

Depending on the engine’s running condition, the voltage on all oxygen sensors typically ranges from 0.1 to 1 volt. Since sensor 2 is behind the catalytic converter, it should give steadier readings of about 0.45 volts while idle or cruising at a constant speed.

For instance, there is no voltage activity coming from bank 1 sensor 2, or the sensor doesn’t react during the lean or rich testing period. In which case, the check engine light will be triggered, and the ECU will assume that there is a problem.

What Are the Signs of a Faulty Bank 1 Sensor 2

bank 1 sensor 2 location

There are several signs of a faulty Bank 1 Sensor 2, which include the following:

  1. Check Engine Light Lights Up
  2. Bad Gas Mileage
  3. Engine Sounds Rough
  4. Car is Getting Old
  5. Failing an Emissions Test

Let’s briefly discuss each one of them:

1. Check Engine Light Lights Up

When a bank 1 sensor 2 goes bad, the most common symptom is the check engine light turning on. However, it should be noted that another issue can also trigger a check engine light with your engine.

These include a broken camshaft position sensor bank 1 or something as simple as a loose gas cap. To be sure, have your car checked by a professional to determine the problem.

2. Bad Gas Mileage

Another issue it shares with a faulty camshaft position sensor bank 1 is the bad gas mileage. Oxygen sensors tend to become less effective in the long run. When the oxygen to fuel ratio gets too rich or too lean, the engine becomes less efficient.

So, if you find yourself spending more money on fuel than usual, it could mean that your bank 1 sensor 2 has gone bad.

3. Engine Sounds Rough

A malfunctioning oxygen sensor can seriously affect the timing, combustion intervals, and other vital functions of your engine. This will cause your engine to sound rough or run irregularly. Other effects include stalling and slow acceleration.

4. Car Is Getting Old

As your car ages, its oxygen sensors can become encrusted with sulfur, lead, oil rash, fuel additives, and other byproducts of combustion that have collected on it through the years. This prevents the sensors from sending signals to the ECU. Using low-quality gasoline or fuel that is not recommended for your car can also cause your sensors to fail faster.

A car that is less than 15 years old should have its sensors replaced every 60,000 to 90,000 miles. That way, it will help reduce pollution and keep the engine running smoothly. If the car is even older, the sensors need to be replaced every 45,000 to 65,000 miles.

5. Failing an Emissions Test

Emissions test failures mainly occur due to a faulty oxygen sensor. If you notice a foul odor emanating from your car, you will need to replace your sensor as soon as possible. Otherwise, it will not only cost you thousands of dollars in car repairs. But you will also risk exposing yourself and your family to carbon monoxide if left unchecked.

Required to Replace to Pass the Smog/Emissions Test

If you have issues with a faulty oxygen sensor, it needs to be replaced to pass the smog/emissions test in most states. You can have it done professionally, but you have the option to do it yourself.

Not Too Difficult to Replace a Bank 1 Sensor 2

Replacing a bank 1 sensor 2 isn’t too difficult as long as you have the proper tools. All that you’ll need is a car jack, jack stands, an oxygen sensor socket, and penetrating oil since oxygen sensors tend to rust.

But then again, if you are hesitant about doing this on your own, there’s always a professional mechanic that you can count on.

What Are the Bank 1 Sensor 2 Fault Codes?

To determine what is wrong with your bank 1 sensor 2, you will need to read the fault codes on an OBD2 (On-Board Diagnostic) scanner. The typical codes that come up on an OBD2 scanner are the following:

P0036Heated Oxygen Sensor (HO2S) Heater Control Circuit (Bank 1 Sensor 2)
P0037Heated Oxygen Sensor (HO2S) Heater Circuit Low Voltage (Bank 1 Sensor 2)
P0038Heated Oxygen Sensor (HO2S) Heater Circuit High Voltage (Bank 1 Sensor 2)
P0041Oxygen (O2) Sensor Signals Swapped (Bank 1 Sensor 2 / Bank 2 Sensor 2)
P0054Heated Oxygen Sensor (HO2S) Heater Resistance (Bank 1 Sensor 2)
P0136Oxygen (O2) Sensor Circuit Malfunction (Bank 1 Sensor 2)
P0137Oxygen (O2) Sensor Circuit Low Voltage (Bank 1 Sensor 2)
P0138Oxygen (O2) Sensor Circuit High Voltage (Bank 1 Sensor 2)
P0139Oxygen (O2) Sensor Circuit Slow Response (Bank 1 Sensor 2)
P0140Oxygen (O2) Sensor Circuit No Activity Detected (Bank 1 Sensor 2)
P0141Oxygen (O2) Sensor Signals Swapped (Bank 1 Sensor 2)

Conclusion – Bank 1 Sensor 2 – What Does It Mean?

Bank 1 sensor 2 is the second of two oxygen sensors on the exhaust pipe. It is located behind the catalytic converter and measures the composition of exhaust fumes.

To summarize, modern car engines come in two configurations. First is the in-line engines which generally have only one engine bank. Second is the V-shaped engines which have two banks.

The side of the V-shaped engine containing the first cylinder is bank 1, while the side holding the second cylinder is bank 2. On each bank, there is an exhaust with two oxygen sensors.

The first sensor, located between the engine and the catalytic converter, is the upstream sensor or sensor 1. Then, the second one behind the catalytic converter is the downstream sensor or sensor 2.

Related reading:

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