Tried installing my old fosgate amp in my 02. Ran the power to the battery and the ground to a bolt behind the seat in the trunk. Ran the remote off the yellow/red switched wire and the loc off the speakers. The amp will not power up. Where could I start to troubleshoot. Its brand new power wire/fuse holder/fuse

Your remote wire that you tapped into isn't enough to turn the amp on. You need 12v for that. If you tapped it off the factory amp, there are two power leads going to it. One is 7v, the other is 4v. I know this because I tried to do the same thing. I wound up tapping into 'diode 2' in the fuse box in the trunk. The amp only works when the car is running because it's a diode for the fuel pump, which is fine with me.

Your remote wire that you tapped into isn't enough to turn the amp on. You need 12v for that. If you tapped it off the factory amp, there are two power leads going to it. One is 7v, the other is 4v. I know this because I tried to do the same thing. I wound up tapping into 'diode 2' in the fuse box in the trunk. The amp only works when the car is running because it's a diode for the fuel pump, which is fine with me.

Diode 2 huh. Lemme go check this out.

Yep that worked like a champ. Thanks

I tried this too.
I don't remember the exact numbers but it was something like, 5k Ohms to ground before you pull the 7V line too low to turn on the factory amp (around 3.5 volts). I couldn't find any relay that was readily available with an input resistance even close to that.
Unless you build something with transistors to power a relay, just tap off the fuse panel.

I used the fuel pump wire in the fuse box too. Works like a champ.