CA Traveler...no, the CBSA agent isn't going to be doing a motor vehicle inspection. If there is a concern, they'd just call the local cops for a stop/check.
A note please about those that preach NO CHIT CHAT...be yourself, because doing otherwise makes you all weird and jittery. They aren't going to drag you out of your vehicle for being nice. I am not suggesting you do a full-on diatribe about the news of the day, but trying to be something other than 'normal' sets off as many alarms as sweating and being evasive.
Gary Haupt