What is Bank 1 and Bank 2?
Bank 1 and bank 2 simply refer to either side of the engine. Check your owner’s manual or a service manual for a positive location of bank 1 and bank 2. Most commonly, bank 1 houses the front most cylinder on the engine cylinder 1, and bank 2 is the opposite side of the engine. Check out the pics below to see several different configurations.
Tech Tip: The front of the engine is not the part closest to the front of the car. It is the side with the crankshaft pulley (also called the harmonic balancer). No matter the configuration of the car, whether rear-wheel drive or front-wheel drive or the position of the engine.
In each of these banks, you can usually find respective O2 sensors. With the exception of some Subarus, 4 cylinder engines only have one bank. You will often see codes that reference bank 1, and there is only one bank to pick from, therefore, bank 1.