you're going to need to scan your instrument cluster. there have been instances where the wire harness out in the hood area rubs through. Also there are times where the soldered pin on the circuit board breaks loose. But by scanning the cluster you can see what the reading are doing.
tech2 is the GM scanner which will have the most information but snap on scanners have a lot of data stream and information now days too. A shop or if you know someone with a scan tool will have to scan it for you. It is not something most people can do themselves anymore. You can't even change the light bulbs in the GM dash units anymore. they're soldered onto the circuit board. As are the gauges too. All integrated
Bad stepper motors in gauges of this make and model. rebuilders are readily available online and maybe locally to you. they replace all of the stepper motors in your cluster and can even change the color of your backlights if you want a custom look. :mrgreen:
while stepper motors do go bad it would be very unusual for them all to go bad and all fail in the same fashion. You have one stepper motor for each gauge. they are all the same inside the cluster but have separate circuit completion points. Also, bad stepper motors wouldn't normally make your lights flash on and off. That being said though, a replacement cluster might solve your problem. Just be aware that it also might not.