What are lean codes: P0171 and P0174 indicate a lean fuel mixture on Bank 1 and Bank 2, often detected by upstream oxygen sensors. Why they matter: Lean conditions can cause misfires, hesitation, ...

Your oxygen (O2) sensors are small but mighty — they help your engine run efficiently, cut emissions, and prevent costly damage. With the right OBD-II scanner and a bit of know-how, you can decode ...