Bank 1 vs Bank 2 | What is bank 1 sensor 2? | What is O2 Sensor?

In most cases, bank 1 and bank 2 imply the sides of an engine but are not as simple as the “right side” of the engine versus the “left side” of the engine. Different cars have different locations of their bank 1 as well as bank 2. Bank 1 is always referred to as the “side” in which the first cylinder is located.

What are Bank 1 and Bank 2?

How To Replace a Camshaft Position ...
How To Replace a Camshaft Position Sensor

Bank 1 and bank 2 simply refer to either side of the engine. Bank 1 is on the side with cylinder 1. Bank 2 is the side with cylinder 2. Most commonly, Bank 1 is towards the front of the car if it has a transverse engine.

The easiest way to discover the right cylinder bank is to check your car’s repair manual. You can also try to find any stamps on the cylinder block or head for any cylinder numbers.

The front of the engine is the part where the crankshaft pulley is. The side nearest the front is not the front of the engine.

You can’t simplify it and say that bank 1 is on the driver’s side or vice versa because different engines can have cylinder 1 on different sides. We drive on different sides globally, so it’s confusing and misleading to guess which side bank 1 or 2 is on.

  • Bank 1 is the side with the number 1 cylinder (Cylinders 1 – 3 – 5 – 7 etc.)
  • Bank 2 is the side with the number 2 cylinder (Cylinders 2 – 4 – 6 – 8 etc.)

Bank 1 vs Bank 2

Some engines are labeled along their blocks, providing consumers with data regarding the engine’s bank orientation. In other cases, locating the factory-specific service literature for your particular vehicle might be necessary when attempting to determine one engine bank from another.

Oxygen Sensor Locations

Bank 1 Sensor 1 Location

A vehicle’s (bank 1, sensor 1) O2 sensor will be located ahead or upstream of the catalytic converter on the bank, which corresponds to the engine’s first cylinder.

This is due to the fact that bank 1 is representative of an engine’s cylinder 1, while sensor 1 serves as an upstream designation.

Bank 1 Sensor 2 Location

A vehicle’s (bank 1, sensor 2) O2 sensor will be located behind or downstream of the catalytic converter on the bank, which corresponds to the engine’s first cylinder.

This is due to the fact that bank 1 is representative of an engine’s cylinder 1, while sensor 2 serves as a downstream designation.

Bank 2 Sensor 1 Location

A vehicle’s (bank 2, sensor 1) O2 sensor will be located ahead or upstream of the catalytic converter on the bank, which corresponds to the engine’s second cylinder.

This is due to the fact that bank 2 is representative of an engine’s cylinder 2, while sensor 1 serves as an upstream designation.

Bank 2 Sensor 2 Location

A vehicle’s (bank 2, sensor 2) O2 sensor will be located behind or downstream of the catalytic converter on the bank, which corresponds to the engine’s second cylinder.

This is due to the fact that bank 2 is representative of an engine’s second cylinder, while sensor 2 serves as a downstream designation.

Upstream vs Downstream

The most common method used to describe the location of a vehicle’s O2 sensor relates to its upstream versus downstream orientation.

O2 sensor location

In the bulk of situations, a vehicle’s exhaust will feature two independent oxygen sensors for each engine bank. One of these two sensors will be positioned before (upstream) the inlet of a vehicle’s exhaust catalyst, while the other will be positioned to the rear (downstream) of this same catalyst.

The terms upstream and downstream describe the positioning of a vehicle’s O2 sensor to the exhaust’s catalyst, considering the direction of exhaust flow. This is most easily understood by envisioning a vehicle’s exhaust as a flowing creek.

A vehicle’s catalytic converter would be located after a particular engine bank’s “upstream” O2 sensor, yet before the “downstream” O2 sensor on the same bank.

How to Locate an O2 Sensor Via OBD2 Scan Tool?

You can also use an OBD2 scan tool to determine the exact location of a particular scan tool. This process is quite easy to undertake, taking only minutes to complete. Additionally, locating an O2 sensor by these means is a rather full-proof method, saving both money and effort by eliminating any chance of mistakenly replacing the wrong O2 sensor.

OBD2 scan tool

Before locating a specific O2 sensor, ensure your vehicle’s ignition is turned to the “ON” position, and the OBD2 scan tool is inserted into its corresponding port. At this point, you can then disconnect each O2 sensor, one by one, while reviewing active codes logged on your scan tool.

As an O2 sensor is disconnected, an “open” or “voltage-high” code should be provided with a corresponding sensor location designation. This DTC should be eliminated after reconnecting this sensor and cycling your vehicle’s ignition.

As such, you can continue to disconnect each sensor (one at a time) until you have positively identified the sensor that you have been searching for.

FAQ Section

What is an O2 sensor?

The oxygen sensor is known as the O2 sensor because O2 is the chemical formula for oxygen. The O2 sensor is used to monitor how much unburned oxygen is present in the exhaust as the exhaust exits the engine. By monitoring oxygen levels, the sensor provides a means of measuring fuel mixture.

Are bank 1 and bank 2 sensors the same?

In most cases, the sensors on bank 1 or bank 2 are the same. However, this completely depends on the car model and sensor we are talking about. You must check your car repair manual to find the answer to this question according to your car model.

Is bank 1 sensor 2 downstream or upstream?

Sensor 1 is the upstream oxygen sensor. It is the sensor that measures the oxygen content in the exhaust, providing an input to the computer, which determines how to adjust the air/fuel ratio. Sensor 1 is the sensor closest to the engine. Sensor 2 is the downstream oxygen sensor.

Where are bank1 and bank 2 located?

Most commonly, bank 1 houses the front most cylinder on engine cylinder 1, and bank 2 is the opposite side of the engine.

What causes an oxygen sensor to fail?

There are no true oxygen sensor cleaners that are safe to put through your engine. While some people choose to remove them and use a wire brush or an aerosol cleaner to remove deposits, we do not recommend trying to clean O2 sensors.

Can you drive with a bad O2 sensor?

Yes, you can drive with a faulty O2 sensor. But you’ll want to change it immediately because otherwise, you’ll be spending more money on fuel, whether during the daily commute or an out-of-town leisure trip, and you risk having to spend more on a new catalytic converter as well.

What are Sensor 1 and Sensor 2?

The sensor number tells us where the O2 sensor or the Exhaust temperature sensor is installed on the exhaust system.

The 1st sensor is located closest to the engine, and the last is located towards the rear of the exhaust system.

Generally, if we are talking about O2 sensors:

  • Sensor 1 = Before Catalytic converter Front (Upstream O2 sensor)
  • Sensor 2 = After Catalytic Converter Rear (Downstream O2 sensor)

Some diesel engines have many exhaust temperature sensors, and they can use sensors 1 – 2 – 3 – 4, etc. In this case, sensor 1 is nearest to the engine and the last sensor in the exhaust system’s rear.

Read More
  1. Causes of Check Engine Light Flashing
  2. What is Engine Flush?
  3. Signs and Causes of Bad Crankshaft Position Sensor
  4. Causes of Rod Knock
  5. Different types of Engines

Leave a Comment