DTC P1171: Lean Exhaust Under Heavy Load: Description
WARNING: This page is about a different car, the 2002 Oldsmobile Bravada, 2002 GMC Envoy XL, 2002 GMC Envoy, and 2002 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.
The Powertrain Control Module (PCM) internal circuitry can identify if the vehicle fuel system is capable of supplying adequate amounts of fuel during heavy acceleration (power enrichment). When a power enrichment mode of operation is requested during a Closed Loop operation, by heavy acceleration, the PCM provides additional fuel to the engine. Under these conditions the PCM should detect a rich condition. Whenever this rich exhaust is not detected, a DTC P1171 sets. A plugged fuel filter or restricted fuel line can prevent adequate amounts of fuel from being supplied during Power Enrichment Mode.