I have a scan tool program that runs on a laptop. It's called AutoEnginuity. It's generic but with optional add-on modules for specific manufacturers. It does everything that the dealers high dollar scan tools do on my F250 Diesel, but for way less money. IIRC, I paid $360 for it. There are other options out there that may be even less money (as in free.) But I don't know much about GM specific scan tools.

AutoEnginuity Link

Kevin
1951 Chevy 3100 work truck
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1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.