Depends on the issuer... If it's a third party, then the dealer is out of his mind for making those claims w/o having discussed this specific case with the issuer;
If the dealer issued it and is recommending an investigation (which is nuts), then there could be a conflict of interest - this is where the state would step in;
If it's a Ford issued warranty, the dealer is nuts.
So who issued the warranty? Dealer, third party, or Ford?
I'd like to know how the dealer can say they could void the warranty, and at the same time say a third party might request an investigation -