2003 Caravan SE with 164,000 km on a 3.3 litre. What would be the most common causes for tripping a P0171 (system too lean) code? I haven't been able to locate any holes in the air intake system. Put in a new air filter while I had it apart and managed to clear the code with a friends Elm327 OBD2 interface. The fix lasted through a half dozen cycles, then tripped again 2 days later. I haven't noticed any loss in performance .... just like to fix little problems before they turn major.