I have gone through the archives and found GREAT information here from users who have taken the Bose wiring harness and spliced in to add an aftermarket subwoofer. I have seen replacing it all together with better amps and subs or keeping it and adding on.
Well, none worked for me. I took the wiring harness:
Red/Yellow - Constant Power
Brown - Ground
Red - Remote turn on?
Both Speaker Wires +/-

I assume that is correct. After cutting my wire harness and running it into my amp - no power. Nothing turns on.
I rewire back to the Bose harness, to make sure I didnt pop a fuse - Bose sub works perfect.
I remove and wire into a different 2nd amplifier I have thinking maybe the amp was bad - no power. Nothing turns on.
I then fear, just by chance, could both amps have gone bad from sitting in storage.... maybe... so I get a third amp I know works. - no power. Nothing turns on.

I am at a loss.
I decided to put it all back together and keep the factory wiring stock with Bose and run a completely 2nd line from the battery alone, new ground, etc to ensure it's working - Guess what? AMP WONT TURN ON. Pain in the butt to get access and it took me 2 hours to wire it all, and still nothing.
I have wired a new power wire to the amp along with a new ground (using the massive bolts under the rear seat). The only thing I still had to do was use the remote turn on from the Bose wiring, which I assume was the red wire? So, i'm thinking that has to be the culprit. Now, some on here have stated the amp for Bose is actually turned on by the signal in the Canbus or something, and if thats the case, what the hell is the red wire? I dont know how to check voltage or use a multimeter to see.

So i'm at a loss - 3 different amps cannot be busted, they all worked fine. So it must be the remote not working. I dont know where else I can tap into, the cigarette 12v in the rear seems to be a pain to access. How can I figure this out?? (I'm ripping my hair out on this one, I've installed a hundred stereos in cars over the years)
It's either the ground or the remote, but I have to think its the remote wire. THOUGHTS?

 

In the first two cases, are you saying those amps have some kind of power indicating LED that never lights up?
Was the car turned on into the ACC key position and the radio on and tuned to something with the volume up?
Some amps don't have LEDs which leads to my second question, what did you hook the speaker output of the amps to?

For your 3rd scenario, did you connect the 12V wire to both the 12V in and the remote in?

It looks like your wiring guess is correct.
The remote wire is not fancy (not canbus), it is either 12V or not, but of course your radio has to be on for the switched/remote wire to be on, and to get sound out of the radio of course.

 

Yes, the car was on, stereo on and the Bose sub works great. My amplifiers have an LED to show "on" and in all 3 cases, trying 3 amps, no lights ever lit up. I cannot imagine I have 3 bad amps, just dont think its possible. I think it's something with the remote turn on wire OR the ground perhaps.
I never connected the speaker wires to anything since I didnt think the amp was working.
When I ran the new power from the + of the battery, obviously that should be working without concern.
When I touch the ground to the chassis, I can hear a slight spark sound. So that would tell me it also seems to be working I guess.
The remote is the only one I cannot "test" and reading before that the red wire "should be" a remote wire, that dpesnt always mean it is. I found 2 posts where even the colors of the Bose wiring harness were different. So i'm guessing.
Using your picture above, I did this exact same thing to 3 of my amps and not a single one turned on. I thought it could be the amp I had was too powerful, but I did try smaller as well and still nothing.

 

As a test, run a separate 12v power wire to the remote turn on on the new amp and see if it powers on. I'm assuming it's not getting the remote turn on signal to fire up. That's the only thing that can be wrong with 3 different amps. I don't know what the small red wire is. If the amp comes on you'll need to find a separate 12v switched wire to connect there as the amp trigger. That's easy to do with a meter. Set it to the DC range scale at something like the 20 or 50 setting (whatever your meter has), put the red lead on the wire you're testing and the black leaf.onnany ground point (any Porsche brown wire, bolt attached to metal chassis or body etc) and if the meter reads 12v that's a hot wire. You want one that reads 0 with the key off and 12v with it on.

 

Okay, I took my voltmeter, turned it to 20 - Black terminal connected to the Porsche Brown ground and Red Terminal connected to the Constant and then small red
With the car OFF:
Power 12V reads about 12.05-12.10V
Red (Remote?) reads about 7.58-7.63V

With the car ON (running and radio on):
Power 12V reads about 14.12V
Red (Remote?) reads about 9.05-9.1V

@Petza914 - I took your advice and ran a 2nd smaller power wire to the amp from the same 12V constant - EUREKA - the amp powered on!!
Clearly not at remote 12V like it needs to be, but what the hell ... others have used this without problem, But I do not get 12v from it. So, where can I get a 12v power source for remote power??

 

That's what I figured was happening. Is there a 12v cigarette lighter outlet connector in the back there somewhere. See if it's switched or hot all the time. If switched you can tap onto that 12v + wire and use that as your remote turn on. There are lots of wires back there behind the side doors. You just need to find one of a decent size that is only hot when switched and tap onto it. It's just a trigger wire so doesn't have to carry significant amperage - that's done by the heavy gauge wiring you've already run.

 

@Petza914 So the Cigarette outlets are a constant power. Thats out. I'm digging around in the trunk area now, the left side just has the compressor and the Bose wiring, so thats out. Now im in the right rear side, there all all sorts of wiring harnesses in there. I would hate to "tap" or cut into one just to test the wire if it's a 12v remote. Not sure if anyone knows what is in there to tell what I could use?

 

Doesn't the compressor only run when the car is on? I know the suspension can move in either direction with the car off, but that's from stored air, so I wouldn't rule out a wire from the compressor side.

You can test any wire just by poking the tip of the meter probe in through the insulation without stripping or cutting the wires. I try to avoid doing anything to those really fine wires in the multi-wire bundles and look for things that are at least 14 gauge to lock onto.

 

Any idea what this is and why someone would have spliced into it? Ive used a wiring diagram I found for a Cayenne (although the 955 model) and it shows a Black/Blue wire is for the rear wiper, connected to Fuse 52 (15amp).
By the way, I have now found out my rear wiper doesnt turn on or work... checked the fuse and it's good.
So if this is the wiring harness for it, someone already tapped into this wire, but I have checked with the probe and no power seems to be running through it. Perhaps that is my problem for the wiper not working AND I could use this for 12v?

Seems odd, the spliced wire goes up into the trunk on the right side, as if it's headed into the top tailgate area. no idea what it's for, but certainly aftermarket of some kind.

 

Unhook that looped around wire, then go check the rear wiper fuse in the fuse box. Replace the blown fuse and see if the rear wiper works with the key on. That would be a good 12v+ switched wire to use providing you can restore power to it. The spliced on wire might be shorted wherever it goes to and why the wiper doesn't work if the fuse blew.

 

@Petza914 So I removed the spliced wire, still no power. I checked the fuse (#52 on the drivers left) but it seems fine. What other fuse could that be for that I should be checking? I'm trying to go through the list of possibilities it could be tied to, as I imagine it's a blown or missing fuse. Most of the diagrams for wiring I have seen say blu/blk wiring is remote power, so this should work if I can find out why I have no power through it currently.

 

#52 is the right fuse. I've heard of the wiring up near the roof hinge fatiguing from opening and closing the hatch numerous times. I wonder if that's what that wire is since you said it runs up to the roof area. Someone may have tried to add a separate connection to the wire bundle upstream of where it's broken to get the rear wiper functioning again by bypassing the broken section. Might be worth following that wire up to its origin point to see if they did the same kind of crappy "twist it around another wire" that they did at the other end, and maybe that connection has come loose.

 

So, the fuses all look good this the 52 spot. I replaced to be sure, but no issues. I removed the spliced wire and checked the voltage, nothing is passing through this. "If" this is the wiper motor controls / wiring, still not sure why nothing is going through it unless there is another fuse i'm not seeing. Again, the wiring diagram I am using is for a 955 and I dont have a 957, could be different.

 

So, end result? Porsche - 3, Human - 0.
I tried 3 days and failed. I cannot find a single remote power wire in the entire trunk area or cargo that has access. I found a couple blue/black wires in multiple wire bundles and everyone I tried to test was a no-voltage wire. Almost all the wiring diagram sheets say blue/black was a remote turn on, but whatever.
I give up. I am ordering a fuse-tap for the fuse panels to add my own wire and just run it to the trunk. No other options besides ripping more parts out and digging through more wire harnesses.

 

Test a couple of the empty ones in the bottom section of the driver's side fuse panel. You may find a socket that gets 12v switched you can plug that tap into. I think that's where I powered my radar detector and dashcam from.