Four Codes All At Once

On my 2001 jimmy 4.3 . My wife was driving the jimmy and she called me and was telling me that all the gauges on the dash stopped working. Come to find out the voltmeter gauge and oil pressure gauge still worked. I had her pull in to the next parking lot she could. By the time she got into the lot the gauges were back on. So she went on her way. Not even a 1/4 mile down the road they went back out. Since then they will work then not work,with out any rime or reason. Also the service
engine soon light is on. Codes I got are 740, 758, 785, 1860. I have seen posts talking about all of these codes ending up being a key switch. But no one has said anything about gauge problems. Any help would great!

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