Hyundai Repair: charcoal canister and canister close valve, 2005 hyundai sonata, gasoline vapors

Question
i have a 2005 hyundai sonata and it was recently hit, leaving me with a broken tail light and slight dent on the left rear, while i was grocery shopping. unfortunately, i was not left a note. the check engine light came on. i took it to the dealer and a purge control valve was replaced. the light came on again; a gas cap was replaced. the light went on again, i'm now being told i need to have a charcoal canister and canister close valve replaced because they've been "smooshed". what do these parts do? and is contingent with the vehicle being hit?

Answer
The canister and close valve are mounted on the left rear of your car where you've reported you have collision damage, so the dealer's explanation is plausible.

The charcoal canister stores gasoline vapors making them available to be burned off by the engine when introduced into the engine by the purge control valve.  The canister close valve serves the purpose of sealing your evaporative system (those components which handle the fuel vapors) so the engine control module (ECM) can test the evaporative system to see whether it's leaking.  If the ECM detects a leak or any other problem with the evaporative system, it will turn on the check engine lamp.