2002 Mitsubishi Diamante electrical problem

There will be two fuse boxes, one inside and one under the hood. It's pretty common today for fuses to blow when the battery is reconnected. That's from the memory circuits in the numerous computers charging up. To prevent this next time, use a "memory saver" device that plugs into the cigarette lighter or power outlet, but be sure those circuits remain live with the ignition switch off. If you must turn the ignition switch on for them to work, a memory saver won't work in them because their little transistor battery can't supply enough current for all the things trying to run. In that case you can connect a small battery charger to the battery cables, and set it on the lowest charge rate. Again, only do this with the ignition switch off.

Relay is doubtful. When multiple circuits are not working after working with the battery, we read that the solution was an overlooked blown fuse about 99 percent of the time. That's why it is necessary to point out that there's two fuse boxes in case you aren't aware of that already.