P0171 Fault on 2002 Nissan Maxima: How to Fix System Too Lean Bank 1
I'm experiencing a P0171 code (System Too Lean Bank 1) on my 2002 Nissan Maxima. My husband and I have already cleaned the MAF sensor and inspected all fuel and vacuum lines. We also replaced the fuel pump and strainer, but the car still runs roughly at idle—like it's not receiving enough fuel or air. Despite these efforts, the issue persists. The engine struggles to maintain a steady idle, and the vehicle frequently stalls. I'm looking for reliable solutions that have worked on similar 2002 Nissan Maxima models with P0171 codes. Has anyone successfully resolved this problem? What steps did you take? Any advice on diagnostics or repairs would be greatly appreciated.
P0171 indicates the engine is running too lean—meaning there's an imbalance between air and fuel. I don't know your technical skill level or tools available, so here are some basic steps to get started: - Use an OBD2 scanner to confirm the code and check for any additional fault codes. - With a noid light, test if the fuel injectors are receiving power (check the red wire for 12V when the key is on). - Measure fuel pressure using a fuel pressure gauge—this can help identify issues with fuel delivery. - Inspect all vacuum hoses and connections, especially around the intake manifold, PCV system, and manifold mating surfaces. A helpful trick: while the engine is running (even if poorly), spray carburetor or brake cleaner at suspected vacuum leak areas. If the RPM fluctuates or increases after spraying, it's likely a vacuum leak. Also, please confirm—has there been any recent work done on the vehicle? Is it stock configuration with no modifications? This helps narrow down potential causes.