This happened twice already over a few months, once while driving in heavy rain and once after the car was parked and locked under a rainstorm. It looks like some electronics reset. While it resets all kind of lights flash and many controls like lock, windows, start, turn signal won't work. After resetting you can get the car to start and it runs fine. Resetting takes a few seconds and during that time the RPM needle drops to zero while the engine is running. The gas level lights cycle up and down with each reset.

Two videos on Youtube:

I did not find any wet spots anywhere in the car. 24 hs later something dried up and all is back to normal.

I run a hose on the car for 1/2 hr today with water running down different sides and nothing happened.

Any suggestions are appreciated!

Thank you!

 

Need a maintenance history. What maintenance was performed on the car before it started doing the light show?

I'd suspect faulty ground connections.

 

Have you checked your battery?
If you have starter cables, try connecting your car to a donor to see whether it has any effect.

 

Multiple systems are being effected IHKS, Kombi, FRM, air bag, etc. All different ecu's in different locations handling different systems. However, they all connect through the junction box behind the passenger side footwell. Check SPEG/Junction box grounds and look for a possible windshield or other leak getting it wet is where I would start.

 

I think Tigger2011's suggestion is not bad, but here is the maintenance history.

September 2017
New Battery OEM.
New spark plugs OEM.
New coils OEM
New brake pedal switch OEM.
Oil change
New air filter OEM.
New footwell controller
New High Pressure Fuel Pump.

March 2018:
Coolant expansion tank.
Front brake disks and pads.

February 2019:

Changed rear shocks and front struts.
Changed all the valve stem seals.
Changed the timing chain rail that was cracked.
Changed the automatic transmission fluid.

 

Thank you Tigger2011 for your suggestions!

The ground connection under the front right door sill cover strip looks good, not loose or rusty. It provides the ground for many of the connectors going to the junction box. No water stains under the front right door sill cover strip or around/below the junction box. I can spray all the connectors with contact cleaner.

Leaks in the windshield are hard to check...

The cowl cover was not well seated against the windshield and had a 1/4" gap in the middle. The rubber lip right over the battery area has a 3" cut where it joins the plastic. If I run water down the windshield a lot gets into the battery space.

I will remove the cowl cover and battery and check/clean the feedthrough behind the battery. That sits right over the junction box.

 

I cleaned all the dirt under the battery tray and the drain holes there are clean.
The cowl cover is well seated.
And it just did it again. There is no water at the junction box, nothing.
It rained all night and the car stood out in the rain.
Today it's much cooler, so it could just be condensation somewhere on the electronics.
I still have to spray all the connectors of the junction box with contact cleaner.

 

I found some corrosion on connector C-A3. Cleaned it and put everything back together.
Time will tell.

 

Two years later update:
The sunroof leaks due to worn seals and the drainage can't keep up with it during a bad storm. The solution right now was to seal it with FlexTape. That tape sticks very well and is UV resistant. Packing tape will only last a month. Two rolls of 4" x 5', cut in half lengthwise with a blade will be just enough.
In addition to that the front plastic clip that holds the roof gutter trim was damaged. The clip sits in a hole in the sheet metal at the top of the A pillar. The water would come in through that hole and out at the top of the interior A-pillar behind the trim. From there is would get into the wire harness that leads it straight to the electronics.
The foam pieces behind the exterior A-pillar trim were also missing. They're also held in place by a few clips that sit in holes in the sheet metal that can provide a quick path for the water to come in. The rubber lip on the exterior trim was also damaged by the sun and a lot of water from the windshield would flow behind the trim.