Changed the timing belt and now the check engine light will not reset.

What is your question?

My mechanic changed the timing belt on my new "gently used" 98 VW Cabrio convertible about 3 weeks ago and the check engine light can't be reset. It's turned off and immediately comes back on. I don't have an operaters manual either that I've been looking all over for. Hopefully someone can steer me in the right direction. Thanks so much.