In this clip, we are going to talk about the proper service procedure in order to diagnose remove and replace your vehicles starter solenoid. In this step we are going to talk about what starter solenoid is and the proper way to diagnose the command wire from your ignition switch. Your stater solenoid is a very heavy duty switch. Now what it does is, it takes the load off of your ignition switch to turn your starter. Your starter is going to run off several hundred amperes of power. If that was loaded through a very small wire and through your ignition switch that would burn it up almost immediately. So what they do is they use this command wire, which runs right from your ignition, to this heavy duty switch. It commands your solenoid to engage the positive from your battery to the positive side of your starter, thus engaging the starter motor. In order to diagnose the rest of the system and make sure it is actually getting the command, what you do is you remove the command wire, you insert your test light into it, and you hook the other lead up to the negative. From there you?re going to hop in the vehicle and turn the ignition key to the crank position; all the way turned. Now as you can see, the light lit up. Go ahead and cycle it a few times. What that does is test the circuitry from this wire from the very point of the solenoid all the way back through the relays and to the ignition switch itself. That is the functionality of a starter solenoid and the proper way to diagnose the command wire.