Check Engine Light '99 Jetta Wolfsburg 2.0

Hi

I've been fighting this light for some time now. It comes and goes..

I've seen the threads on this problem it doesn't seem to really have a cure.

I had the car in yesterday for a radiator hose repair and the mechanic noticed the "check engine light."

He ran a check on his diagnostic machine and found the following error message.

17990 IDLE SPEED CONTROL
ADAPTATION AT LIMIT
(P1582) ERROR OCCURS INTERMITTENT

Does anyone know how serious this is? Cost to repair?
Will the car pass an emissions test?

Thank you!!