Wiring problem for after market backup camera

This system has been seriously complicated with computer controls and digital signals. You are going to have to take some voltage readings to see if there is a circuit that can be used.

Look at the center tail lamp assembly. It should have three black wires going to it. Measure the voltages on those wires with a digital voltmeter when the back-up lamps are on. If you find twelve volts on two of those wires, you should be able to use either one of them.