Back in February purchased a 2013 Lexus GS 350 AWD from a iaai auction (the long island location, NY). Had a minor damage on the front end mostly cosmetic, aside from the steering airbag being blown, replaced most of the front end including the fender, hood, headlights, bumper sensors, radiator, upper rad support, steering airbag, and I've got the airbag module reset. The car was a salvage title, through inspection and got a GA rebuilt title, since I've bought I put 6,000 miles on it, but every once in awhile driving it I would get the "check AWD system", plugged in a Snap-On scanner, and the code came out to c1299.
Going down the list there's no oil coolers or transmission coolers in the front so I doubt any oil with leak out or anything like that, usally that msg would pop up after driving the car on "unsafe roads".
Just looking for some insight, wisdom, and maybe a solution to the problem, the car drives perfectly fine, but it's a bit unsettling having that message pop up on the dash every once in awhile.

 

I had this when I destroyed an ABS/speed sensor on the rear hub.

If it were mine, I'd check all the wires for the ABS/speed sensors, starting with the front that had the most damage. It might be loose or have a frayed wire from the impact.

Good luck.