Code P0171 — System Too Lean (Bank 1)

The P0171 code indicates that the engine air/fuel mixture is running too lean on Bank 1 (the side of the engine containing cylinder #1). Too lean means there is too much air and not enough fuel in the mixture. The ECM is adding more fuel than expected via long-term fuel trim to compensate, indicating a real underlying problem. This can lead to engine damage if the lean condition is severe or prolonged.