...but the engine wasn't running.

I turned the key to the "On" position and was ready to wait for the little light to go off, the speedometer and the tachometer both pegged at their topmost extremes - in unison. Then they both settled right down to zero again. My overhead MPG reading also dropped from the mid-18's to 15.0. Nothing else seems to have happened... elapsed time continues to run, tripmeters didn't reset, etc.

Any ideas on why both of my main dash gauges would have pegged in unison like that?

 

Your truck is trying to tell you something, "Drive me fast, Drive me fast" ks

 

was your trip meter reset button on the cluster pressed somehow??? if you press and hold the trip meter button on the cluster, and turn the key to run, you will run the instrument cluster diagnostc test... all the lights light up, all the gauges sweep from end to end..

 

Nope, mine were the only two hands in the cab at the time - one on the wheel, the other turning the key. The tripmeter button isn't stuck "down", either.

 

Mine did that once before. Got in the truck and turn it on and all the gauges did a full sweep. Wasn't touching anything?? Not sure what caused this but it was something. Oh well trucks fine, I'm not loosing sleep.

 

Did it reset your overhead MPG, too?

Mine acts almost like it lost the most recent reflash and reverted back to its original programming. The overhead MPG readings have dropped back to what they used to be prior to the most recent reflash. Actual mileage doesn't appear to have changed, just the readout.

 

Some cars will do this when there is a low battery, or poor connection/corrosion at the terminals. Not sure on the dodge trucks, but I know it happens on fords.

SQ