well, my 99.5 a4 has about 91k and im not even shure if the owner before replace the timing belt or waterpump. i was just wondering what is the first thing i can check and do, with out getting rip off because my engine light recently just turn on.

 

If it has 91K Km, it is unlikely that he replaced the timing belt or water pump.

If your check engine light came on (yellow pictogram of the engine), then you need to pull the codes with a vagcom or go to autozone and have them pull the codes for you.

If you mean the reminder that says "service", that just means that you have exceded the miles since the last service interval/oil change.

 

Does it hesitate or feel like its running rough? Could be somthing simple like O2 sensor. In 3 different vehicles I've had when the check light came on, that was the problem on all 3. All were between 85,000 and 95,000 miles. Simple and cheap fix.