Why Your BMW’s Check Engine Light Isn’t Always What It Seems

Your BMW’s check engine light comes on. You take it to a parts store, they plug in a scanner, and you walk out with a piece of paper that says something like P0171 — System Too Lean, Bank 1. So now what? Most people assume the code tells them what’s wrong. It doesn’t. It tells them what symptom the engine management system detected. The difference between those two things is exactly where BMW repairs go wrong.