Had my belt replaced and the guys tore the upper radiator hose on a 99 XJ and doused the bay with coolant. I got a no buss no gauges but the car ran fine. Drove it about 100 miles. Then the gauges came back, engine light was on and showed 2 codes, Cam sensor and p1391. Opened the hood and found the hole in the hose and coolant all over the bay. Replaced the hose. Would throw both codes every few days intermittently. Always ran fine. No more gauge problems. So I replaced the cam sensor. Now it just throws p1391 intermitantly.

I figure something got wet and corroded a bit by the coolant.

But what?

Ground points? Is there a ground that serves the gauge cluster and cam sensor?

Also it only throws the code when the weather is wet.

Thoughts on where to start?

 

https://m.youtube.com/watch?v=K5f7FnhE5cc

You can easily remove the cap for he distributor to allow it to air dry and check for residue of coolant. The link above talks about replacement. The distributor is right below the heater hose. This makes sense as a repercussion. I'm not sure that the 1999 is like my 1992, though. You may have some coil-on-plug fanciness.

 

An easy thing to try is the 3 connectors going into the ECU at the front left of the engine bay. I had intermittent bus errors and gauges not working when it was damp out. I disconnected them after disconnecting the battery and sprayed them with contact cleaner. I also removed the gauge cluster, and did the same thing. The ECU plugs are the easiest, and since you had a lot of coolant spill there I would try that first. Probably wouldn't hurt to do any other connectors that got soaked. Good luck.