Are you struggling to find out which O2 sensor you should replace?

You are not alone! Everything with bank 1, bank2 sensor 2, etc., can be really confusing when diagnosing your car.

The truth is that it is actually not that difficult! Lets find out!

What is Bank 1 vs Bank 2?

Bank 1 Vs Bank 2

Bank 1 and Bank 2 refer to different sides of the engine. Bank 1 is the side with cylinders 1, 3, 5, 7. Bank 2 is the side with cylinders 2, 4, 6, 8.

The easiest way to find out 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 located at. The side nearest the front is not the front of the engine.

The real truth is that 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 just really confusing and misleading to guess which side bank 1 or bank 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.)

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What is Sensor 1 & 2?

Bank 1 Vs Bank 2

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

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:

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

Bank & Sensor Conclusion

O2 Sensor On Cat

Bank 1 Sensor 1 is the first sensor closest to the engine. Located on Bank 1 means it is located at the engine side with cylinders 1, 3, 5, 7, etc.

Bank 1 Sensor 2 is the second sensor on the engine’s exhaust pipe, usually behind the catalytic converter. Located on Bank 1 means it is located at the engine side with cylinders 1, 3, 5, 7, etc.

Bank 2 Sensor 1 is the first sensor closest to the engine. Located on Bank 2 means it is located at the engine side with cylinders 2, 4, 6, 8, etc.

Bank 2 Sensor 2 is the second sensor on the engine’s exhaust pipe, usually behind the catalytic converter. Located on Bank 2 means it is located at the engine side with cylinders 2, 4, 6, 8, etc.