You still need to clear the code after putting your cap back on

At the shop I work at, we would take a peek at 90k on a newer car and service it if its in bad shape, otherwise leave it. And the shop I work at is the biggest and busiest non corporate shop in my (big) city.

You should always specify what kind of car you have and what year when asking questions like this. All cars are not created equally or the same.