[BNaylor]

The reason why the lights (SVS, ABS and TRAC OFF) come on when you are moving is that is when the ABS system initializes and runs a self test. There must be motion to check the ABS wheel sensors. From all indications it looks like one of your wheels has a bad hub/wheel sensor. Determining which one is the hard part and normally diagnostics should be run with an ABS capable scanner. Autozone scanners cannot read out GM ABS/Chassis codes.

Another thing you can do with a DMM is ohm out each wheel sensor and check the electrical connector/wiring at the back of each hub. Look for around 1K ohms resistance across the wheel sensor contacts hub side.