What does a P1171 code mean for a 2000 Volvo S80?

A P1171 code for a 2000 Volvo S80 indicates a problem with the fuel trim, specifically that the engine is running too lean. This means that the air-fuel mixture has too much air relative to fuel, which can lead to performance issues, increased emissions, and potential engine damage if not addressed. Common causes include vacuum leaks, faulty fuel injectors, or issues with the mass air flow sensor. It's advisable to diagnose and fix the underlying issue to ensure optimal engine performance.