Diesel Bombers - 03 Gauges going nuts

Hello,

My instrument cluster is going crazy on my 03 Ram 2500, 5.9 HO, NV5600 4x4.

The check engine light comes on randomly for a second or two, then the volts/oil pressure/coolant temperature gauges will all quickly drop to zero, then slowly sweep back to where they were before -- and then the check engine light turns off again.

Sometimes, also, the fuel gauge (independently of the other gauges) will drop to zero and the fuel light will come on, and a chime sounds. Then, usually but not always, the gauge will sweep back to where it was and the fuel light will go off. When the fuel light is on, the AC compressor cuts out and will only come back on when the gauge sweeps back and turns off the fuel light. Also, when this happens my overhead computer blanks out (just dashes for the average fuel economy and distance to empty).

Also, sometimes both the tachometer and speedometer will drop to zero and then sweep back to where they were.

I also get blinking ABS and airbag lights randomly.

When we recently drove to Tucson from Albuquerque, this all happened over and over for hours. Then eventually the entire gauge cluster went dead (no gauges at all). I pulled over and disconnected both batteries for ten minutes, and that got them working again, but that just started a new cycle of the gauges going crazy. I ended up having to use my phone's GPS to figure out how fast I was going.

These behaviors seem to have no relationship to temperature (has happened on very cold mornings before the engine is warmed up, and also happens on hot (90+) afternoons with the engine at full operating temperature). The behavior is completely random, as far as I can tell. It happens more frequently when driving at high speed, but it also happens sometimes when the truck is sitting at a stop light. This morning it started happening immediately after starting the engine, after the truck had been sitting for more than twelve hours.

Here's the troubleshooting I've done:

I did a test of the instrument cluster (hold the odometer reset button while turning the key to On) and all lights illuminate and the gauges sweep just fine.

I removed the gauge cluster from the dash and used electronic contact cleaner on the male and female end of its three connectors. This had no effect.

Any suggestions where to go from here? I'm pretty certain there's nothing wrong with the gauge cluster itself. Would these problems be caused by a bad ground somewhere, or does it seem more likely my ECM or PCM are faulty?