It’s important to know which bank (or cylinder head) is number one to help determine a starting point for firing order or just to replace the correct part, like an Oxygen sensor, fuel injector or ignition coil. In the past all that was needed to determine which bank or cylinder head is number one was to see which cylinder head is positioned the farthest forward. The one that is the most forward (closest to the front of the engine) is the number one cylinder and that side is bank one. But many engines today have cylinder heads that are positioned evenly, which makes it harder to determine which is bank number one and which is bank number two. A couple of common reasons we need to know this, for instance is to determine Oxygen sensor to replace when you are looking for B1 S1 (Bank One Sensor One), or if you’re trying to locate an ignition coil to inspect for a P0301 (#1 cylinder misfire recorded) misfire code.
Things to try
1. Four cylinder engines always have the #1 cylinder closest to the front of the engine (only one bank).
2. V-6 or V-8 look for the plug that is closest to the front of the engine, if the cylinder heads are even an alternate way of determining #1 will be required.
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