What is bank 1 on 2001 Ford Mustang?

On a 2001 Ford Mustang, Bank 1 refers to the cylinder bank that contains cylinder #1. In a V6 engine, cylinder #1 is typically on the passenger side (right side in the US). In a V8 engine, it's also generally on the passenger side. The specific location might vary slightly depending on the engine configuration, but it's always consistently referred to as Bank 1.