That's a EVAP vent system performance DTC that is purely emissions. You have a clogged vent valve and canister. You need both as well as the updated filter and relocation kit. Your username says it all....under vehicle dirt, mud, debris, and mostly DUST clogs up the stupid EPA crap on these trucks but the updated kit should keep you clean.
BTW.....not sure where you got the description of the DTC....but there are other DTC's that are associated with an electrical malfunction (as this is a mechanical malfunction) than P0446. If it's a hand held tuner or info from AutoZone, I'll sleep better tonight.
P0446 is set when the EVAP is not able to vent quickly enough.
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