Test Description

WARNING: This page is about a different car, the 1995 Oldsmobile Ninety-Eight and 1995 Buick Park Avenue. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Test numbers refer to numbers on diagnostic chart.

Visually/physically checking components/systems which may cause a lean condition may determine cause of Code P0171.
MAF sensor which causes PCM to read a lower than actual airflow can cause a lean condition, and Code P0171 to set.
Check for faults in EVAP purge system that may cause Code P0171 to set.

Fig 1: Code P0171 Schematic (3.8L) Fuel Trim Lean

Fig 2: Code P0171 Diagnostic Flow Chart - 1 Of 2 (3.8L) Fuel Trim Lean

Fig 3: Code P0171 Diagnostic Flow Chart - 2 Of 2 (3.8L) Fuel Trim Lean