as said above....

 

I think you are talking about the selenoids in the rat's nest. How they work is simple, with the EGI main relay switch, eg car on sometyimes key on, all the selnoids get B+, or 12v, they are turned on by the ECU grounding the other side of the selnoid, thus drawing current. If you want to test them out of car, just slap a battery to them, if you want to test them on the car, turn key on, and ground out the negative side at ECU terminal or selenoid. Really handy if you can't get to it, just look up ECU pin, and ground it with key on, and listen, or 'T" and test vacuum lines, etc.