(Pt 1) "Cadillac Expert"...has NO CLUE!! ('17 CTS: Beached Whale, NO-COMM when WET?)

Customer dropped off his "Possessed" 2017 Cadillac CTS with only 60k miles on it. He said during the WET Spring the Caddy would randomly leave him STRANDED, go into LIMP MODE while driving, and would not crank if he shut it off. He took it to a local "Cadillac Expert" 3 times, and the "Expert" said he might need a new ECM, Alternator, and "Startup Control Module"....hahahahahahahahaha xD However, now it's nice and dry and warm, and the Cadillac drove to my shop with absolutely no issues or warning lights. Are we going to have to wait until the winter to reproduce the customer complaint?? With 30 computers onboard, finding an extremely intermittent Network Fault could be MISSION IMPOSSIBLE! But let's take a stab at it anyways and use wiring diagrams and COMMON SENSE to possibly find the Needle in the Haystack... TOPDON Phoenix Plus: https://www.amazon.com/dp/B091BQNR3S?... AstroAI Digital Multimeter DVOM: https://www.amazon.com/dp/B07FDBW1PT?... ATD Tools 5513 Heavy-Duty TEST LIGHT: https://www.amazon.com/dp/B000M5ZWBA?... Enjoy! Ivan