Check engine light is on and idle is fighting the brakes. What is the cause? on 1999 Volkswagen Jetta

Is a constant problem. Don't know diagnostic codes.

Asked by for the 1999 Volkswagen Jetta
Is there any noticable 'hissing' inside vehicle when brake pedal depressed? Maybe brake booster is bad causing a vacuum leak- that could cause high idle and difficulty braking.
1 more answer , 2 more comments
What do you mean when you say the idle is fighting the brakes, and was the check engine light on before the brake problem occurred?
When stopped at a stop light, the rpms increase and the brakes must be pressed harder to keep it from moving forward. I'm not sure about when the engine light came on. I am dealing with second hand information from my out-of-town daughter.
Most places like Auto Zone, Napa, and Advance auto parts will scan a car for the engine light codes for free. Get her to do that and let me know what they say. With little information though, It sounds like an air leak is causing an erratic idle speed. Ask her if the engine RPMs rise and fall when the car is in park, or if its only with drive engaged.