Bank 1 vs Bank 2 – Sensor 1 & 2 (Locate O2 Sensors Fast & Easy)

When reading the trouble codes with a scanner, it can be difficult to figure out what the trouble code means. Here is what you need to know about bank 1 and bank 2

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Are you struggling to figure out which O2 sensor or ignition coil you should replace?

You are not alone! Using a diagnostic scanner can really help you troubleshoot a car’s issues efficiently, but sometimes it can be difficult to know what the trouble code you read from the scanner actually means.

One of these things is if you get a trouble code saying bank 1 or bank 2, sensor 1 or sensor 2 in the last sentence of the trouble code data. But, It is actually not that difficult! Let’s find out what it means!

What is Bank 1 vs Bank 2?

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 just 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.)
bank 1 vs bank 2

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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 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. On Bank 1 means it is 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. On Bank 1 means it is at the engine side with cylinders 1, 3, 5, 7, etc.

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

Written by:

Magnus is the owner and main author of MechanicBase. He has been working as a mechanic for over 10 years, and the majority of them specialized in advanced diagnostics and troubleshooting. He has also been a motorsport (drifting) driver for over 5 years.