2000 Chevrolet Malibu P0171 Code: Diagnosis and Solutions for Lean Mix Ratio
I've already replaced the fuel filter and both O2 sensors (Bank 1 and Bank 2), but the P0171 lean code persists. Below is my freeze frame data: - Fuel System 1: CL (Closed Loop) - Fuel System 2: NA (Not Available) - Calculated Load %: 6.7% - ECT (Engine Coolant Temp) °F: 143.6 - STFT Bank 1 %: -0.8 - LTFT Bank 1 %: 21.9 - MAP (in inches of mercury): 14.2 - Engine RPM: 1,479 - Vehicle Speed (MPH): 48 - MAF (Mass Air Flow) lb/min: 1.4 - TPS (%): 4.3 I'm currently troubleshooting this issue and would appreciate any guidance from experienced users on how to resolve the P0171 code in a 2000 Chevrolet Malibu.
Refer to common causes and solutions for P0171 trouble codes in this forum. For a lean condition like P0171, first check for vacuum leaks or inaccuracies in the MAF sensor or fuel delivery. To test for a vacuum leak: observe the LTFT (Long-Term Fuel Trim) value at 1479 RPM. It should decrease when engine speed increases and rise slightly at idle. Hold the throttle steady at 2500–3000 RPM for 20–30 seconds. If the LTFT drops to around 10%, this suggests a vacuum leak. If the trim remains unchanged or increases, then consider issues with the MAF sensor or fuel pressure. Given that the MAF reading appears accurate and assuming normal fuel pressure, focus on locating potential vacuum leaks in the intake system.