The amp is on the passenger side in the cargo area.
There are two fused +12V supplies to the amp.
Central Junction Box, F41, 5A, a yellow & red wire to the amp
Engine Junction Box, F69, 40A, a fat red wire to the amp
These feeds are on different plugs at the amp, the main power feed is the fat red wire, the "wake up" is the smaller yellow & red wire.
With the truck on, you should see 12-14V at the connector for each of these wires. On my truck, I was only measuring .7V on the yellow/red wire (so the amp would not turn on). So somewhere between the central junction box and the amp, something went bad.
My fix was to make a jumper from the 12V signal on the sat radio over to the yellow/red wire at the amp connector (cut the yellow/red wire, isolate the end that heads back to the CJB so you don't risk causing a future short, then connect your jumper to the end still attached to the connector). With it like this, the amp turn-on is now running off the sat radio fuse, but I haven't had an issue for the 5 years I've been running like this.
Rich