An oxygen sensor also called O2 Sensor or lambda sensor (λ) is a device that measures the concentration of oxygen in the exhaust gas of an internal combustion engine. The oxygen sensor provides information to the engine control unit (ECU) that is used to optimize the air-fuel mixture.
The ideal air-fuel mixture is stoichiometric, which means that there is an equal number of atoms of oxygen and fuel. When the air-fuel mixture is too rich (too much fuel), the engine runs inefficiently and produces excess emissions. It is located in the exhaust manifold before and after the catalytic converter.
The catalytic converter can be placed on side of the engine called a bank. Luckily, here we will deeply discuss the banks of the engine.
In this powerful guide, you are going to learn about bank 1 and bank 2, O2 upstream and downstream sensors, how to know bank 1 and bank 2, and many more things.
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What Are Bank 1 And Bank 2 Oxygen Sensor
In the automobile world, the bank means the side of the engine. Bank 1 indicates one side of the engine, while bank 2 indicates the other side of the engine. Usually, bank 1 is the side with cylinders firing orders 1, 3, 5, and 7, and bank 2 is the side with cylinders firing orders 2, 4, 6, and 8.
Bank 1 is the side that starts with cylinder 1 (Cylinder 1, 3, 5, 7….).
Bank 2 is the side that starts with cylinder 2 (Cylinder 2, 4, 6, 8….).
The side of the cylinder depends upon the make, model, year, and engine. The oxygen sensor’s location is divided by position sensor 1, and sensor 2.
A four-cylinder engine or inline six-cylinder engine has only one bank. So, all the oxygen sensors will be located on bank 1. “Bank 1 sensor 1” indicates the front sensor, while “bank1 sensor 2” indicates the rear sensor.
A V6 and V8 engine has two banks, “bank 1 sensor 1” and “bank 1 sensor 2”, which refers to the front and rear sensor with cylinder firing orders 1, 3, 5, 7, etc.
Similarly, “bank 2 sensor 1” and “bank 2 sensor 2” refer to the front and rear sensors with cylinder orders 2, 4, 6, 8, etc.
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The side of the engine is referred to as a bank
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O2 Upstream Sensor
The oxygen sensor located before the catalytic converter is called sensor 1. Sensor 1 is the front sensor before the catalytic converter (Upstream O2 sensor).
Sensor 1 is also called the Upstream or Pre-Cat Sensor. It is the oxygen sensor located before the catalytic converter close to the engine on the exhaust manifold.
This sensor is used for regulating the air-fuel ratio of the exhaust coming out of the exhaust manifold. It measures the level of pollutants in the engine’s exhaust to adjust the air-fuel ratio.
Downstream Sensor
The oxygen sensor located after the catalytic converter is called sensor 2. Sensor 2 is the rear sensor after the catalytic converter (Downstream O2 Sensor).
Sensor 2 is also called Downstream or Post Cat Sensor. It is the oxygen sensor located after the catalytic converter close to the muffler on the exhaust manifold.
This sensor monitors the efficiency of the catalytic converter. It monitors the level of pollutants passing through the catalytic converter.
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Both front and rear sensors work together to maintain the air-fuel ratio and the input of both sensors is compared by the ECU and decide the amount of air-fuel to be allowed to the engine cylinder.
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How To Know Bank 1 And Bank 2
People get confused about how to tell which is bank 1 and bank 2. Below are the three methods of knowing bank 1 and bank 2.
1. By Reading Car’s Owner’s Manual
A good way to know the right cylinder bank number is to check the car owner’s manual.
2. By Letter Stamp On Cylinder Block
Sometimes, a mark or letter is stamped on the cylinder block, or the head indicates the cylinder bank number.
3. By OBD 2 Scanner
You can use an OBD 2 scanner tool to know the right bank number. First of all, make sure that you do not have trouble code, if so, then erase all the code. Unplug any of the oxygen sensors on any bank. Now, a trouble code appears, It will show you the oxygen sensor with the bank number.
Bank 1 – Sensor 1
Bank 1 sensor 1 is the front oxygen sensor on bank 1. The bank 1 sensor 1 oxygen sensor is used to monitor the oxygen concentration in the exhaust gases. It produces voltage and sends it to the car ECU, which increases or decreases the air-fuel ratio.
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Bank 1 – Sensor 1 – Location
Bank 1 sensor 1 is located before the catalytic converter. A four-cylinder or inline six-cylinder engine has one bank, so it is located before the catalytic converter, near the engine under the hood.
If the car has a V6 or V8 engine, then bank 1 sensor 1 is located before the catalytic converter at the engine side with cylinders 1, 3, 5, 7, etc.
Bank 1 – Sensor 1 – Upstream Or Downstream
Bank 1 sensor 1 is an upstream oxygen sensor. It is also called Pre Cat Sensor. It is the sensor located before the catalytic converter on bank 1.
Bank 1 – Sensor 2
Bank 1 sensor 2 is the rear oxygen sensor on bank 1. It is used to monitor the efficiency of the catalytic converter in the exhaust gases.
Bank 1 Sensor 2 Location
O2 sensor Bank 1 Sensor 2 is located after the catalytic converter on bank 1. A four or six-cylinder inline engine has only one bank so the O2 sensor bank 1 sensor 2 is the rear sensor located after the catalytic converter.
A V6 or V8 engine has two banks, so bank 1 sensor 2 oxygen sensor is located after the catalytic converter at the engine side with cylinders 1, 3, 5, 7, etc.
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Bank 1 Sensor 2 Upstream Or Downstream
Bank 1 sensor 2 is a downstream oxygen sensor on bank 1. It is also called a Post Cat Sensor, located after the catalytic converter.
Bank 2 Sensor 1
Bank 2 Sensor 1 O2 sensor is the front oxygen sensor on bank 2. These sensors are not found in inline-four or six-cylinder engines. Bank 2 comes in V-Shaped engines such as V6 or V8 engines.
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Bank 2 Sensor 1 Location
Bank 2 Sensor 1 oxygen sensor is located before the catalytic converter. A bank 2 sensor 1 O2 sensor is located at the engine side with cylinder orders 2, 4, 6, 8, etc.
Bank 2 Sensor 1 Upstream Or Downstream
Bank 2 Sensor 1 oxygen sensor is an upstream oxygen sensor. An upstream oxygen sensor is also called Pre Cat Sensor which is located before the catalytic converter on bank 2.
Bank 2 Sensor 2
Bank 2 sensor 2 oxygen sensor is the rear oxygen sensor on bank 2. Bank 2 Sensor 2 is found on V6 and V8 engines.
Bank 2 Sensor 2 Location
Bank 2 Sensor 2 oxygen sensor is located on bank 2. A bank 2 Sensor 2 oxygen sensor is located after the catalytic converter at the engine side with cylinder orders 2, 4, 6, 8, etc
Frequently Asked Questions (FAQs)
There are typically two banks in an engine, referred to as bank 1 and bank 2. Bank 1 is typically the side of the engine that contains cylinder numbers 1, 3, 5, and 7. Bank 2 is the other side of the engine that contains cylinder numbers 2, 4, 6, and 8. The terms “bank 1” and “bank 2” refer to the two halves of the engine where the cylinders are located.
Bank 1 is the designation for the side of the engine that contains cylinder number 1. The position of bank 1 is not fixed; it can be on the left or right side of the engine, depending on the specific engine design. When discussing the positioning of bank 1, it is important to note that its position is not fixed. Rather, it can be located on either the left or right side, depending on the particular vehicle. Therefore, when asking whether bank 1 is on the left or right, the answer is that it depends.
In automotive engineering, the term “bank 1” is the name given to the side of the engine where the cylinders are numbered 1, 3, 5, 7. Bank 1 is not a device, it is the name of the side, on the other hand, the catalytic converter is a device located on the side of bank 1 or bank 2 depending upon the make and model.
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