2003 Mazda Protegé 5 P0171 Oxygen Sensor Too Lean Bank 1 - How to Fix?
My 2003 Mazda Protegé 5 has the check engine light on, showing fault code P0171: 'Oxygen sensor too lean bank 1'. I took it to an auto shop where they asked if it's upstream or downstream. I'm not familiar with these terms and don't know which one applies to my vehicle. Can anyone clarify what upstream/downstream means in this context? What are the common causes and solutions for P0171 on a 2003 Mazda Protegé 5? Any advice would be greatly appreciated.
Start here: https://www.obd-codes.com/p0171. Common fixes include cleaning the Mass Air Flow (MAF) sensor and checking for vacuum leaks. These are typical solutions for P0171 in a 2003 Mazda Protegé 5.