Replacing OEM bose stereo with MOST box

So before I embark on this journey I kinda want to make sure I've got what I need... I have an 09 Cayman base with the bose sound system . I found a good deal on a double din pioneer android auto head unit and I'd like to try and install it. Given the price of the Nav TV unit, however, I instead went shopping on alibaba and ended up with a generic MOST box "Designed in Germany, Assembled in China" that shipped to me in a phone case package. Off to a great start! But hey the $80 vs $700 made it worth a shot... Naturally it comes with no instructions. But it seems pretty simple. My only concern is that it seems like I should need more wires than this. Maybe... Notably the wires coming out of this most box are a red and white RCA cable marked Aux In R and Aux In L, and then there are wires for ground, accessory power and battery power. This is the thing I bought: https://www.aliexpress.com/item/RCA...Porsche-fiber-optic-power-amplifier-to-aftermarket-Car-DVD-GPS/32708723316.html This is probably a long shot but I'm wondering if anyone knows of any instructions on how to hook this sucker up or what other parts I may need... I'm feeling like this might be more of a pain that I anticipated and I'm wondering if it's worth it now... I don't really want to have to splice into OEM wires or anything here but it's looking like that's what I'd need to do... Starting to think running new wires and speakers would be easier but that's not much fun either.

Not sure what the NAV-TV module has to do with your Pioneer install? To me it looks like the MOST box requires the normal assortment of power connections, the RCA's are connected to the stereo output of the Pioneer head unit , the OEM fiber optic interface connects to the MOST box ... This allows you to retain the BOSE amplifier and speaker system, the amplifiers in the Pioneer system will not be used.

Right I get that, what I'm confused about and can find no real instructions or videos on, is how to actually wire it up. I mean I need to find power, ground, accessory, illumination, etc wires somewhere. And crutchfield says there is no wiring harness for my car. I take that to mean I'd have to find those leads...somewhere in there and splice into them. Or run wires from the fuse box or something. I suppose the big question I haven't found by browsing other posts is, can I just buy the wiring harness adapter for the non Bose version of my car and use that to get power, ground, accesory, illumination, etc?

It looks like you have 3 wires and 2 RCA's. The RCA's are easy - they go to the back of the new head unit. Metra makes a wiring harness adapter to replace the standard non- bose unit . It works for the bose as well - sort of. You'll want to remove most of the pins because you wont use them - leave the power and ground. The yellow wire will need to be run straight to the fuse box by the drivers left foot (fuse B-9 IIRC), buy a mini fuse tap to make the job cleaner and easier. The black and the red will line up with the power and ground of the harness adapter and the new head unit.

I am sort of midway through my stereo install, and haven't gone back to it in months. I keep not wanting to leave the car in an unfinished state, so I left it in an un-begun state. You might find info to be helpful from these pages: https://cai-store.com/pages/hur-installation https://www.planet-9.com/987-cayman...n-and-boxster-electronics/233407-ae0273b-08a-install-2006-porsche-cayman-s.html I bailed out on the Longate MOST adapter from Alibaba (still have it unused) and decided to get the https://www.spiralaudio.com/index.php?route=product/product&product_id=990 since it provided some OEM harness interfacing that the Longate does not. But still not a true plug & play solution. You'll need to find wires or signals for: reverse toggle (if you use backup camera) illumination dimming Constant 12V Switched 12V Ground Your installation kit may provide some OEM ISO harness interfaces. I used this for my installation kit: https://www.amazon.com/dp/B00EUJENGE As Jim Roal pointed out in his thread, the Axxess AX-LDBK line filter may also help the audio quality of your replacement head unit. Let us know how it goes and good luck.

So today I broke it open to see and this doesn't seem to be the case... Crutchfield said to use the Metra 70-9003 harness, which is for 2002 and up audi/bmw/vw. I bought the scosche vw-3b instead, same harness but with some more pins. But looking at the photos and the one I got they don't fit at all. The pins are lined up the wrong way and in no way align with the slots. View attachment 205087 Is this the wrong harness? I can't really find anything specifically for the car (2009 Boxster base).

I bought the Axxcess adapter kit for my 987 with Bose Fiber Optic and it works great. The same kit is about $250 on ebay.

Seems like a better option though cheapest I can find it is $316. Have to think about whether it's worth the money to not have to splice wires...

You might find this thread useful. https://www.planet-9.com/987-cayman...xster-electronics/231490-sony-xav-ax5000-seicane-most-installed-987-2-bose.html

Does Axxess AX-LDBK have the same function as MOST adapter Fiber optic converter for Bose Amp?

How did this install turn out?

I did a great deal of research on this. I had a 2004 Boxster Special Edition and there were no alternate wire harness systems for the MOST radio for that year and older. There is no alternative but to remove the Bose Amp and Head unit and replace with an aftermarket system. You don't really need an AMP, you can just use the Head Unit to power the existing speakers; but remember the Bose speakers are most likely 2 Ohm and will need to be either replaced or wired differently to compensate for the Head Unit; depending on the head unit input requirements. It may be compatible with 2 ohm speakers. The speaker connections with the MOST system most likely assemble by the amp in either the frunk or under the pass. seat. Then there is an optical connector which goes from the head unit to the amp. You'll have to pick up the speaker wires from the amp and then run them to the dashboard to be wired to the head unit. I wrote an article on installing an aftermarket head unit into my 2013 Boxster and it absolutely rocks; but thankfully, I had the base radio.

So I kinda gave up on this because it seemed to much of a pain / expense. Now my shift cables snapped and I've got everything tore open again and I'm tempted... again... I gave up before when I tried to order the AX-PO904 adapter from some website and they told me it'd be months before they could get one. Best buy sells them, but for $400... Seems like it'd be easier to just replace the speakers and run new wire to them. I'd lose out on the bose rear speaker box but, is that really much of a loss? The down side is I still haven't found a wiring harness adapter so I'd have to splice everything in which I hate doing. Still debating if it's worth it...

I believe this adapter will work for the bose amp: https://www.installer.com/item/display_item.php?it=ct20po01

Nope, that's definitely not it. My plug looks like this:

Right, I was talking about the plug for the amp in the trunk.

So I decided to dive back into this. I found an Axxess AX-PO904 interface for $260 in stock which was a pretty good deal. I did get the backup camera installed last night and that wasn't too bad. I had the center console out to do the shift cables so I routed the wire along the center and then along the bottom of the rear wall carpet, up along the passenger side of the engine bay. There was a plenty big gap along there into the trunk, and with popping a few plastic pieces it was easy to fish it into the trunk. Then I had to pop out the taillights and remove the rear bumper. Also not really difficult. I didn't fully remove the bumper, but I did take all the bolts out (T40 torx). WIth that I was able to pull back the top of the bumper enough to route wires. I drilled a small hole above the license plate and got the camera mounted and tightened down and then ran it through the bumper and up below the taillight into the trunk. The new head unit arrives today so I can hopefully plug it all in and see how it works!

Further update: I do not see any possible way the AX-PO904 hooks up to my car. The connectors are all different. Despite it saying on the box that it fits 911 / Boxster/Cayman up to 2014. Doesn't help that there are zero instructions on it but I don't see any way it can possibly plug in to what I've got... Now I've got about $800 worth of stuff sitting around rather useless... Doesn't somebody make an adapter that just works?

So after mulling this over I have decided to try to wire it up the hard way and if I can't, then give up. Hopefully I can return the Axxess adapter... My plan is to use the cigarette lighter wiring in the passenger footwell to power the stereo (I planned to replace that 12v outlet with a dual USB outlet anyway), then tap a fuse in the fuse box for a switched 12v. Then I guess I'll have to run a wire back to the taillight to get a reverse signal. Hopefully I can find an illumination wire somewhere or if not just skip it. I have a parking brake bypass for pioneer units so I can use that to avoid running a parking brake wire, or just actually run the wire, either way. That *should* get me all I need to work with the alibaba MOST adapter I bought long ago though it's going to be pretty hackey. But I don't see a better way...

I think I'm just blogging my adventure to myself at this point but hey, might help someone in the future. I've had moderate success! This is temporary just figuring out all the wiring. I did find my old scoche wiring harness adapter did kinda work after all. However it also only seems to give me battery power, ground and remote turn on. I can't find an illumination wire or a switched power. I've run a switched power from the fuse box. Still hunting for illumination. For the backup camera I tapped into the right rear brake light. Brown wire = ground, blue/black wire = power. The camera I bought has the red wire running up to the front too so I hooked that up to the reverse input on the stereo. And I also wired in a parking brake bypass. So audio works, backup camera works, everything has appropriate power! Now I just need to find illumination and then permanently wire in. And try to find the antenna adapter I bought and see if it works at all (I've got a bad feeling about it). Also if anyone wants to buy an Axxess adapter for...some other bose equipped car that is apparently not mine (I suspect it's for the 987.1 bose cars) lemme know I'll make you a deal! Update: found a little led light on the wiring in the center console, I think it lights up the ashtray, so I just tapped the wire on that for illumination. This was a lot easier for me since I already had the center console out to do the shift cables, maybe not so easy for for someone just doing the radio.