Hello, "Protect" is an indicator that there is a fault in the speaker outputs of the Kenwood. Either one of the speakers is blown, has a wire touching the chassis of the vehicle, or on of the speaker leads coming out of the radio are shorted somewhere in the vehicle to chassis, or the other lead of speaker wire. Try disconnecting all of the speaker leads from the radio and isolate them from each other with electrical tape. Then try to power up the system again. If the "Protect" is gone, then try connecting the speakers one at a time, powering off the radio while connecting and then powering back on after each one is connected. As soon as one of the speaker wires causes "Protect" to come back on, THAT will be the faulty lead/or speaker. If the unit shows "Protect" with no speakers connected, then the speaker output MOSFET inside the unit has shorted and it is need of repair. I can send you the contact information for a service center if you'd like.
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