Yellow Relay

[RAYLEE29]

Hi,it could be the fuel pump relay. The sierra loom is quite modular so its reasonably easy to remove sections such as abs central locking windows etc etc i think the fuel pump relay is part of the engine loom comes just after the big ecu plug
hope this helps otherwise check the wiring colours and look in the manual at the wiring diagram
if you dont have a haynes manual i could look it up for you but ill need the car model year and engine size/type plus the wire colours for the relay
Ray