This is from my C9 manual, and together with Mike’s post should serve you well:
Joel
There are several pages of flash codes. Let me know and I can look up what you get, or I’d guess you can check CAT’s site and drill to them. There is a diagnostics port for the engine and one for the tranny under the removable panel in the dash top in front of the steering wheel, and ports in the battery bay. Qualified CAT technicians can access ECM fault from either location.