Random shut down

[robert3rekab]

It's a pleasure to be here and thank you for allowing me to join the forum.

I have an '09 pro star ISX 15 with 800,000 miles on it and it's been very well maintained. The truck was accidentally left outside for two days with the hood open in heavy rain and now it has random shutdown. Could happen with initial startup of the day while idling or even anytime driving down the road. That's real sucky because I have to try and always make sure I'm driving on the right hand lane in case I have to pull off! one time it shut off just by pressing in the tractor air brake release button. After sitting on the side of the road for a few minutes it will start back up and runs smooth as ever.... until it randomly decides to shut down again. It's like a total electrical power loss the dash just goes blank and the engine shuts off.

Any of you pros in here know of this situation can help me please?!!
Thank you, Robert