it might have actully happend at 20k miles because is time for your 20k maintenance! take it in! nothing should be wrong.. just needs to have all its bolts tightened and checked out !but as for if there is an erroru got obd-II so that means u cant do it alone, you have to goto a dealer and get it checked out! or goto a autozone or local car place, they usually do free error code readings to hopefully sell u parts..