Peterbilt 357 wiring diagram need

Hi everyone. I am new to this forum. A good neighbor has a 2006 Peterbilt Dump 357 and has had since new. He does nearly all of his own work on this but is now stumped by a wiring nightmare trying to figure out why his dash guage lights every fifteen seconds all turn off and their red warning lights come on, they go back to normal and repeat that cycle endlessly. We suspected the black VDO box, inspected the circuit board inside with magnifiers for burnt reistors or expanded capacitors, all of the printed circuit board looks fine.

He has pulled all dash modules out looking for a sign of the cause of the problem, but without any clues. He's brilliant with mechanical stuff, rebuilding engines, rear ends transmisions, anything except admits he hates wiring and has lost his cool over it. Two of us neighbors have tried looking for the problem for a time, but nothing has solved this intermittent glitch.

We are handicapped a bit without having the wiring diagram for the 2006 Peterbilt 357 model. Would that be the same as anything in another numerical family of Peterbilts? I did run across a wiring diagram for a 359, 379, other numbers which I've read may all be in the same family that includes the 357.

By the way, what is the difference between a 357, 359 and a 379? I've read they are all in the 379 family.

Does this describe a condition any of you have any ideas on, or experienced yourself?

All that is left up our sleeve is to take each connection behind the dash apart and look for corrosion and perhaps put a dab of conductive gel in each electrical contact point socket.

Any links to a great source of Peterbilt 357 wiring digrams would be very much appreciated.

Is the 359 close enough to the 357 that we would be able to use it? I did find a PDF on the 359.

Thank you in advance for any suggestions on this mystery electrical problem.

This photo is the label on the black VDO box containing the circuitry which we believe may control this strange symptom.