Question

How do I solve the engine code P0171 on my 2001 Toyota Corolla?

Answer 1

P0171 Fuel system too lean

Some of the causes lean condition are vacuum leaks, most common are at the MAF (Mass Air Flow) air duct which tends to get torn and give false air which sets a lean code condition

Answer 2

P0171 Toyota Code - Fuel Trim System Too Lean Bank 1
Read more: https://www.autocodes.com/p0171_toyota.html