Initially, my 2000 Ford Focus displayed only P0141 and P0171 fault codes. I replaced the spark plugs, spark plug wires, and one of the oxygen (O2) sensors. After retesting, the same codes—P0141, P0
I currently have a P0171 code on my 2000 Ford Focus SE. I've already replaced the fuel filter, both O2 sensors, spark plug wires, and plugs. I plan to replace the PCV valve before resetting the code. Is it located on the valve cover? I followed the hose from the air filter box to the valve cover but don't see a removable component there. Any guidance would be greatly appreciated. I've purchased a new PCV valve—any advice on how to install or use it? Thanks.
Which O2 sensor was replaced and what brand did you use? The P0136, P0141, and P0171 codes are related to post-catalytic converter oxygen sensors. Please verify the wiring, fuse, and connection integrity at the sensor. A lean condition (P0171) may resolve after addressing the O2 sensor issue; however, if the code persists, check for vacuum leaks. Good luck—please update us on your progress.