That's the first time you mentioned check engine light which is kind of important information. You need to explain the problem better in more detail and exactly what is happening. When you say buzzing, do you mean the beeper is going off? Is it constant, or a long beep every minute or so? Do you get any message on the dash like OIL with the check engine, red light flashing? What makes it go away? Does it start, idle, and run fine? Have you pressed set 5 times while it is beeping to get a code?
With your current description, I can limit it down to about 200 possible issues.