On some 2012-2013 Acura ILX, MDX, RDX, TL, TSX and ZDX models, the stock gas cap can cause codes P0455 (EVAP system large leak) and/or P0456 (EVAP system very small leak detected). The gas cap may also be loose or have a stick-slip feeling when tightened.
The cause of the codes is a fuel fill cap gasket creates too much friction, preventing the cap from sealing properly. If the gasket is brown, the fuel fill cap has already been replaced. If the fuel cap has a black gasket, replace it with one that has a brown gasket.