AnthonyGS

I recently acquired one of my all time dream cars. A 66k mile 91 ZR-1 with a lot of the normal C4 problems. This forum has been invaluable helping with issues and I will have them all sorted by Christmas.

This post is needed because I had to search all over including other forums to find my Bose answers.

At first I bought a CDM and spare Bose amps. I spent quite a bit and the "good" cdm is also not good. I did find out I got a free top gun cd and foreigner cassette when I tried the new cdm but alas no tuner or sound.

I had disconnected all four amps as recommended in case one was bad too. I've also been working on instrument cluster issues so my whole interior is a mess.

So after research you can integrate the Bose amps and speakers with a aftermarket head unit (any brand you like) by using a metra bypass harness. Harness number is 70-1857. I learned that here. This harness will provide power, antenna power, antenna reception, grounds and provides RCA cables to adapt to the Bose amp/speakers.

The connections for this harness are made at the CDM (varies by year and GM car). For that reason the harness is long..... Too long. I did surgery on the harness wires but still have a ton of RCA line to hide and antenna wires.

With just my alpine head unit and the metra harness, I used the RCA outputs on the rear to drive the Bose amp/speakers. Sounds easy right? It was, but this setup led to a horrible pop every time I changed radio stations upon startup and shutdown, when switching to cd, etc. POP, POP, POP..... This is caused by the delay literally shutting off and reporting the Bose amps all the time. It is super annoying. Some people live with it. You do not have to!!!! I did find out with this setup all my Bose sparked/amps are good.

Research.... Lots of cars have Bose systems. Some guys are.using caps, filters, noise filters, or delays to get rid of the pop. There is a super easy and cheap way. I used two PAC sni-35 signal converters. These are wired to the speaker outputs and reduce the head unit speaker level power to a low level RCA signal. I am using these RCA signals (which are adjustable) to drive the Bose speaker/amps. With these two black boxes and the metra harness I now have perfect righteous sound from my Bose speakers with decent bass too!!! Yes really. Total cost with a 175 head unit will be around 250. I probably should gone double din on the head unit. I may later but I like the cubby too. I used the metra kit with harness and install plates. Car removal disassembly covered here many times. I do have a few key photos though.

Metra harness attaches at cdm plugs and antenna. Simply remove from CDM and plug in. My CDM was under glove box. Other c4s have them in rear cubby.




Three CDM plugs and antenna plug into metra bypass harness.

On the opposite side of the harness that attaches to your head unit you will attach power wires, ground wires, and two pac sni-35s. RCA cables will plug into pac sni-35s. This will provide a nice low level signal to Bose speaker/amps. Be sure and test fade and balance to insure L/R F/R all works properly. I actually tested all the wiring in the passenger seat before routing.




Testing wiring in passenger seat. Wiring plugged into back of head unit sitting in seat and other connections at CDM.

Look at that huge loop of extra wire laying in the floorboard. Here is a photo of wire I removed. I wish I were skilled in cutting and shortening RCA lines but since they are shielded I keft them 17 feet long..... I removed about 1 lb of copper wire.




Extra wire removed.

Here is the harness after surgery.




Harness ready to install.




Final head unit install.

Tunes!!! I have tunes!!! The ride control is fixed thanks to the forum. Light clears when car is moving. I do have the low tire pressure system to deal with still.

Z51JEFF

Getting the CDM controller out of the car is a nightmare,good luck.