Instrument panel lights flashing

[GTOWag]

I accidently held the reset button in on my tripometer while turning on the ignition key to the run position. Suddenly all the instrument panel lights started flashing and all the gage and speedometer and tachometer needles were swinging back and forth. After a few seconds things went back to normal and the truck runs fine. I asked the service writer at my local dealership and he basically said "DUH". Can anyone tell me what just happened?

 

[bighammer]

It's a self-check sequence for gauges, lights, etc. Pretty cool, eh?