ESP light on, message that it malfunctioned
 

I have a W204 C300 sport 4matic. I am rebuilding this car, as I purchased on a salvage title from an insurance auction.

The car was hit in the front left, cracking the wheel, damaging the front left strut and putting a slight bend somewhere in the steering rack.

I have replaced the wheel, though there is currently no TPMS sensor in it so I am getting the warning light there.

The car has been aligned and is in spec.

I have not done anything to the steering rack yet, as I was advised to leave it alone unless I am really bothered by the very slight binding feeling you get when turning the wheel a certain way.

However, when I drove the car for the first time after doing the various repairs, about 10 minutes into the drive, the ESP exclamation point light came on, with a dash message that the ESP system had a problem and was deactivated.

What controls that system? What sensor or part is sending that signal? In other words, where do I start repairing it? I have not put my code scanner on it yet to see what I get.

Please help!
-David

You really need to pull codes before you do anything else. :)