How are we supposed to help without any useful information?
Head unit? That's a stereo. Bad info on your part.
He probably meant the DME, but how are we to know? Aftermarket? Is there even an aftermarket unit that'll work with this car? I don't know.
You need to:
1) find out what the problem is and get back to us using the proper terms.
2) do some investigative work for yourself. Get in there and look at the unit. Is it OEM?
If you do #'s 1 & 2, you will probably find that you've answered your own question and are wasting our time with questions that we could have no way of answering since you failed to provide the necessary information and we cannot see your car.