What is the wiring diagram for a 1998 SABLE stereo?

Not sure. If you are hooking up an aftermarket stereo, I recommend going to Walmart and buying a harness adapter. This will make sure the connections are correct and you won't have to compromise the existing wires. The WalMart harness uses a universal color-code that adapts to any aftermarket stereo and, worst case scenario, you can deduct what factory wires do what and then you can return it back to the store once you have your diagram. Hope this helps.

Cheers,

Chrestmaker