: Complete Bose Removal in '99 STS

03-28-09, 09:22 PM
Hi, I've been reading over the forums for some help finding the appropriate wiring harness for my vehicle.

I have put complete stereo systems in my 2 previous Cadillacs which were a '91 Coupe DeVille and a '93 Sedan Deville with no problem but the STS seems to be a bit more complicated with the computer issues involved.

If I am COMPLETELY removing the Bose equipment and installing my own Head Unit, Amps and Speakers is the GMRC-03 what I need to install to not have any problems? I have seen people talking about relocating the factory HU but can't tell if that is only done in the "cheapskate" setup.

I would really like to be able to install this as cleanly as I did my previous installs by simply using the appropriate wiring harness. I've searched these forums but can't find a thread talking about a complete removal and replacement with aftermarket equipment. I have only found threads talking about an integration with the Bose system which is not what I am doing.

Son of BTN

I do not have On Star.

03-28-09, 09:40 PM
you will most likly have security and sleep mode issues...all the GMRC does is let you keep your chimes; nothing more,
To elimiante all problems you need to relocate the head unit to the trunk and run your constant & switched 12 v. as well as ground and dataclass wires.

03-28-09, 10:09 PM
Thanks for the reply but I have read a lot of hearsay and need something concrete so I can get started on this install.

Has anyone actually replaced their entire factory Bose system and if so is your factory HU still hooked up in your car somewhere?

I have been looking at the Sevilles on cardomain.com and have seen some cars with their factory HU still in the vehicle while others seem not to be.

03-28-09, 10:34 PM
i have done several conversions....there are several variables, its like the sleep mode, some people never see it and so they swear it does not exist...this would be true if the car was driven ever day, but let it sit for 24 hours and you will notice it.
the "concrete" side of it is the BCM expects the radio to be in the loop, if it is not you WILL get some sort of malfunction; how annyoying it will be will depend on your some of your personal habits and the way your car is used.

03-29-09, 12:55 AM
I have the Seville which seems to be completely different than the DeVille's setup. I found this post in another thread:


must be a lot different in a '99 deville than in my '01 seville. i installed an Alpine HU no problem, replaced front speakers with an Infinity Component set, put up some 3-way Infinity 6x9's in the rear deck and spliced in the existing BOSE speakers in the rear doors to the same rear channels. cost of installation was around $250 because the entire car was re-wired front to back but the stock HU is collecting dust in my closet not piggy backing in my trunk...was something changed over the years?

03-29-09, 01:01 PM
the seville is slightly different, but the basic vehical data system is the same....the extent of your symptoms will vary with the use of your car.
I gave up working on car audio professionally several years ago, now days I will only do work by referall, and when they are looking for something totally custom. I can honestly say that about 90% of the work I have done on 96 and newer caddies are people I talk to about it and either try it themselves or go to best buy or audio express and try to get the work done....I''ll clean up the work just for the "told you so value".

I dont mean to come off as a smart ass, but pull your head unit out and look for the two dataclass wires (i believe they will be purple and purple white), if they are there then there is another computer in the car expecting to talk to it, alot of people have mentioned shortcuts, or half assed work arounds (connect the wires together, the GMRC, etc), yes , these will make it function, but sooner or later you will start noticing quirks.

03-30-09, 02:22 PM
I'm going to cave and just stuff the factory headunit in the dash or trunk somewhere. It's not worth finding out about problems down the road that don't even need to be there in the first place.

So should I still be using the GMRC-03 harness but rewire it slightly to accomodate the data wires running to the factory headunit? I really would prefer using some sort of wiring harness rather than splice everything directly to the car.

03-30-09, 05:24 PM
trust me, the caving will save you a potential mystery and headach in the future. the way I have done it in the past is to create a second pigtail harness donated from a junkyard car, so you can basically Y off with the cables you need to run back. The stock chimes originate off of the front left speaker output of the stock head unit. you can either tie in the GMRC or add a dedicated speaker for the stock head unit FL chaannel and stash it in the dash.

The only things you need in the back are the switched and constant power, ground, and data, The fastest and cleanest method I have found is to pull a front seat, and the complete rear seat...this lets you run the wires under the console, to the back, and under the trunk carpet. from there I usually stash the head unit in the spare trie compartment..out of sight.

04-27-09, 07:57 PM
i pulled all my bose speakers in my 96 seville, stuffed my head unit in the space in front of the console, and found my signal and power wires right off the factory head unit wiriong harness. i tried removing the head unit completely but my battery kept going dead, and removing fuses to prevent this also required i go without things like my power windows, etc. the cars been going now 2 years no mystery quirks with a clarion dvd player and all aftermarket speakers. i left the bose amp and other wiring in place in case the computer was still communicating with it, and made sure my factory hu was turned off while stashed away. the only thing i sacrificed was a ducting plenum to move air to the rear heating, but the heat still finds a way back there thru the vents. it may be heating the area behind the dash as well, which i thought may overheat my aftermarket hu, but so far no problems.

i read another closed thread where someone did exactly what i did, seems a headache free way to go, instead of fighting with aftermarket wiring adaptors that dont seem to work. like timothyr says, a way to improve on this is to get a long harness to relocate the factory hu to the trunk to preserve the ducting. last i checked it was a few hundred bucks.