Connect the short black wire to the GND- on the amp. Pinch the other end of the black wire under the bolt next to that wire loom.
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Connect the red wire to the Positive battery terminal with the fuse holder on that end (leave the fuse off). Connect other end of red wire to the +12V on the amp. Connect the yellow wire to the REM on the amp.
Now here is the difficult part. With a multimeter, check those wires for a 12 volt signal that goes "off" when the ignition is turned off. The black lead on the multi will go to the grounding bolt for this test. When 12 volts is found, that is where the yellow wire will be connected as well.
Now switch multimeter to OHMS. Wrap one of the factory wires to the black lead of the multi. Now touch red to other wires until one reads 2 to 4 ohms. Tape those together, they go to the factory speakers. There should only be one or two sets.
Now switch multimeter to AC millivolts. With the radio on, wrap one of the remaining wires to the black lead, now connect the red lead to other wires until one shows voltage. That will be the partner of the other. Now find the other set. These will be the music signal.
Those sets will be wired to a harness that came with your amp. It plugs into this white inlet.
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Now, connect only one side and install fuse by the battery. Turn radio volume low and amp gain about 1/4 way. Now connect other set of wires to the white plug, if bass lessens, swap wires. But if bass goes up, you are set.
If you can make sense of all this, awesome. Keep us posted.