What is Bank 1 and Bank 2?
The term "Bank" on automotive is used by the manufacture to identified the side of the engine. For example, on some vehicles "Bank 1" is assigned to the left side of the engine, if there was a problem with the oxygen sensor on the left side of the engine, the manufacture definition for the engine’s left side Oxygen Sensor would be "Oxygen Sensor Bank 1".
Manufactures identified the engine sides differently. Some manufactures may assign the left side of the engine as Bank 1 and the right as Bank 2. The best way to determine which side is Bank 1 or Bank 2 is to check the vehicle's service manual. On most vehicles Bank 1 is referring to side of the engine where the #1 cylinder is located.