I needed to replace the relay for the A/C located on the fuse block in the DS kick panel and noticed that along with the two spaces shown in the FSM and Elec FSM (A/C relay and Engine Cooling fan) there were 2 additional spaces for relays. Does anyone know wht there were / are for? Also what is the ECM 2 fuse in the dash used for? It's been unused since I bought the truck.