What does gas cap have to do with fuel tank pressure? on 2001 Honda CR-V

I was recently told that I needed a new gas cap; all I got in explanation was that it had something to do with the pressure in my gas tank. I had taken the car (2001 Honda CRV) in for the required annual inspection sticker. What are the consequences if I don't get a new gas cap?

Asked by for the 2001 Honda CR-V
gas cap seals like any other cap, the evap sys on your car at times builds pressure in fuel sys to ck for leaks and must hold pressure for a period of time to pass test. if any seal is bad light will come on and trip a code.hope this helps
This was very enlightening. So apparently one of the items on the checklist for these inspections is the evap system; they found the tank didn't hold the pressure adequately and pinpointed the gas cap as the problem even though the light has not yet come on to warn me. Thanks so much.
Just in case the light does return , post the specific coe. The CVS (canister vent shut-valve) and the two-way by-pass valve and solenoid are two other common problems on this model. can involve a little time to properly diagnose which one (or both) is/are bad. Has your CR-V ever been bumped or hit in the fuel tank filler neck area? ..............HOPEFULLY it's just the cap! AND hopefully they replaced it with a Honda cap. I've seen a few aftermarket caps that don't function the same as OEM.
1 more answer , 1 more comment
Its part of the evap system. It will most likely turn on the check engine light when cars computer checks the system. Its a sealed system with a purge valve if the cap seal is worn or the cap is not on tight enought it will triger the light. if the lights not on wait till it comes on.
Thanks so much. Because the light has not come on yet, I was surprised and confused; your answer was very helpful in determining what to do next.
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