Bob, I have a very similar problem, almost exactly what you were having; same deal, the dash goes dark, all the warnings, my lights even would flash on and off sometimes along with my wipers because of the wiper settings in EVIC when wipers on, headlights on too.
I had a body ground issue in my IHS CAN circuit; one of the components had poor ground, which was intermittent.
First, check batteries and grounds as we have a known poor ground on the left frame horn on the driver's side in front of the LH wheel.
My final conclusion was a ground on the inside kick panels; it sounds like all your IHS CAN issues and the lost comms code are showing up.
Pull covers off on RH and LH kick panels; there is a rubber sound-deadening mat, lift it up a little, and you will see a ground bolt (10MM) and each side; this was where my issue was.
It was clean and dry, with no corrosion, but I was able to tighten them down a bit and never had an issue again.
It was intermittent, which made it tough to locate.
I would lose my power windows, mirrors, and door locks.
The rear windows still worked, and the gas gauge dropped to empty, TPMS warning, etc.
The IHS is the internal high-speed CAN; you have about 5 CAN systems and a few LINS; I know you have a CAN and a CAN2 for engine control; IHS runs a combo meter, so this is where all the warning lamps are, and when it goes down, all goes nuts.
Anyway, good luck; intermittent issues can be tough; this is where a nice scope to see waveforms for the CAN system comes in handy; I posted up the one I got when chasing this issue down.
We have a STAR connector where you can unplug branches from the CAN, and when the offending one is disconnected, the system returns online; it's a bunch of small 2-pin connectors in a block, LH side of the dash area.
I think this was made to allow techs easy diagnostics.
Location of STAR connector on a 2019, maybe the same area, never mind the Neanderthal arm, it is not me; if it were, I'd shave them.
Bookmarks