Well first the good news. I replaced my radiator and the leak has vanished. Yay.
The bad news: A few days later I'm driving from work to my GF's house. Pretty typical mix of traffic/highway. It's nice weather out so I'm driving in Comp mode just in case I find an open spot to have fun. It's more optimism than anything else, as I drive that same route all the time and there is never a place to have fun lol.
Anyways, with comp mode on I'm sitting at a stop light. My service stability system notification kicks on the screen. I acknowledge it. At that point, my T/C light is still on, as I was in comp mode. I turn TC back on, then try and go back into comp mode but it won't let me. It's either on, or off. I drive to her house, park it for the night.
The next day it drives perfectly normal. No service stability message, no TC lights, works in comp mode, etc. Everything seems fine.
A day later (this AM) I was driving home going down the highway at about 60mph with the cruise set. I feel a loss of power, or almost felt like a light tap of the brakes and the the stability system engaged message appears. No T/C or ABS lights or anything. I didn't hit a big bump or anything, the road was smooth.
I press the TC button to kick the light on and disable everything. Or at least that's how I believe I disable everything.
Regardless, about 5 minutes later I'm still cruising, T/C off, cruise control on, but not engaged (power button on, don't have it set to maintain any certain speed). I feel another tug, and the stability system engaged light comes on. The tugs are very brief, like a quick light tap on the brakes. But it's unnerving to say the least.
From the posts I've read, common culprits seem to be the Steering wheel position sensor, the yaw position sensor, or the wheel speed sensors. Anyone have experience to say that one or the other seems to be the usual suspect? There was a guy on the Cadillac forums that described almost my very problem, and for him it ended up being the SWPS. I'm almost tempted to change that before going to the dealer and paying 90 bucks for a diagnosis.
Any thoughts? Sorry for the wall of text