I have problem with my oem sub and amp. It´s not working for long time but I want to solve it now. But I don´t know where is the problem. I have the RNS-D navi plus, 4 speakers and sub in a trunk. I tried to measure the voltage, when radio is turned off i can measeru 12V on connector to amp but when I turn on the radio there is 0V. Where is the problem?