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I just checked the DropBox, there are 5 tunes for 2002 Commodores there. I'm betting there's something behind the scenes that's causing these issues, I'd start with a bone stock, 2002 Commodore file and go from there. It wont give you the 12212156 OS, but 12225074 is a well supported OS as well. You can run COS3 with that OS and it is the proper base OS for your vehicle.
I dont see the 12212156 OS being used on any Commodore per the DropBox, however that could be incorrect as I've never seen one in person.
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There is COS5 for these two GM OS's:
- 12225074 Holden LS1 2002-4 -> upgrades to COS5 01290005
- 12212156 Camaro/Firebird 2002 -> upgrades to COS5 02020005
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There you go, use the 12225074 as the base OS and you should be set.