P0171 Fault Code on 1998 Nissan Altima: Diagnosis Tips and Common Fixes
I'm experiencing the P0171 diagnostic trouble code on my 1998 Nissan Altima. I've already checked for intake leaks using BrakeKleen, and no visible leaks were found. The O2 sensor readings appear normal according to the scan tool. However, I'm unsure what the next most likely cause could be before disassembling components unnecessarily. What are the top troubleshooting steps recommended for this code on a 1998 Nissan Altima?
P0171 indicates a system lean condition. Check O2 sensor readings — are they stable and within expected ranges? Can you verify if the signal is responsive or erratic? Also, evaluate fuel trim values: long-term and short-term. If the engine is overcompensating, that may point to an issue with fuel pressure. Fuel pressure should be checked as a key factor in diagnosing this code.