You're gonna get the book of opinions on this but let me ask for some clarification.
what do you consider minor mods?
There is really only one absolute at this point... and it isn't even applied universally.
Tunes. GM's, not the dealer's, official opinion is that if you tune the car the power train warranty is done. And that is only if they ask for a scan of the ECM. So a dealer can go ahead and fix your car with a tune if they want to... as long as GM doesn't ask them to produce a ECM scan prior to reimbursing the dealer for the repair....
EVERYTHING ELSE is almost always up to the dealers service manager... A good service manager can find a way to fix your car under most circumstances... even Supercharged cars at times... Not for a blown motor but maybe a transmission??? or half shaft??
So there are a ton of variable to what is or isn't fixed. It really depends on the dealer service manager and his desire/ability to jump through the necessary hoops to get GM to reimburse for the repair.
My best shot at an answer...
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