Living without a CDM
Thread Starter
Race Director
Joined: Dec 2006
Posts: 10,383
Likes: 4
Living without a CDM
First let me share a leaked memo that may or may not have come out of a GM exec office circa 1990.
Now, is there any reason to leave the CDM in when replacing the Bose with an aftermarket?
I have read conflicting posts here that say it is needed for some pass-through data and some say it isn't.
<Excerpted> We have some bad news. It seems that a master gynecologist with robotic Japanese schoolgirl hands and x-ray vision endoscopes has successfully removed the CDM in under four hours. We will therefore bolt on a useless aluminum box to the back of the CDM to take up precious maneuvering space during its removal.”
I have read conflicting posts here that say it is needed for some pass-through data and some say it isn't.
Thread Starter
Race Director
Joined: Dec 2006
Posts: 10,383
Likes: 4
So I found out that with the CDM unplugged that there is no power to the dash and the car won't start.
If I keep only the two inboard plugs attached the dash works and the car runs fine. This lets me use the metra harness (outboard plugs) to connect to the aftermarket head unit no problem.
But what is so key about the CDM?
Is there a single wire or adapter that I can use to bypass to allow CDM removal?
I know there are several people who've made track cars and know this.
Any thoughts?
If I keep only the two inboard plugs attached the dash works and the car runs fine. This lets me use the metra harness (outboard plugs) to connect to the aftermarket head unit no problem.
But what is so key about the CDM?
Is there a single wire or adapter that I can use to bypass to allow CDM removal?
I know there are several people who've made track cars and know this.
Any thoughts?
Racer
Joined: Sep 2006
Posts: 289
Likes: 0
From: Newark DE
Don't you have a FSM? Should be in everyone's toolbox..
My car has a Central Control Module (CCM), but since you refer to a head unit, it also has a radio receiver box and radio control head.. Can't really find a CDM but maybe it's what youre calling the radio receiver under the RHS dash?
There's the TSB about resistors on the CCM dimming controls to the radio control head when removing it for an aftermarket head unit, so if you've done wiring for that you may have inadvertently placed a dependency on the receiver for power ?
Getting into a bit more detail of when the prob started and what was done during that time will help. The FSM may explain it also if you trace the connections. Using the correct terminology from the FSM also helps keep everyone on the same page.
My car has a Central Control Module (CCM), but since you refer to a head unit, it also has a radio receiver box and radio control head.. Can't really find a CDM but maybe it's what youre calling the radio receiver under the RHS dash?
There's the TSB about resistors on the CCM dimming controls to the radio control head when removing it for an aftermarket head unit, so if you've done wiring for that you may have inadvertently placed a dependency on the receiver for power ?
Getting into a bit more detail of when the prob started and what was done during that time will help. The FSM may explain it also if you trace the connections. Using the correct terminology from the FSM also helps keep everyone on the same page.
Thread Starter
Race Director
Joined: Dec 2006
Posts: 10,383
Likes: 4
Don't you have a FSM? Should be in everyone's toolbox..
My car has a Central Control Module (CCM), but since you refer to a head unit, it also has a radio receiver box and radio control head.. Can't really find a CDM but maybe it's what youre calling the radio receiver under the RHS dash?
There's the TSB about resistors on the CCM dimming controls to the radio control head when removing it for an aftermarket head unit, so if you've done wiring for that you may have inadvertently placed a dependency on the receiver for power ?
Getting into a bit more detail of when the prob started and what was done during that time will help. The FSM may explain it also if you trace the connections. Using the correct terminology from the FSM also helps keep everyone on the same page.
My car has a Central Control Module (CCM), but since you refer to a head unit, it also has a radio receiver box and radio control head.. Can't really find a CDM but maybe it's what youre calling the radio receiver under the RHS dash?
There's the TSB about resistors on the CCM dimming controls to the radio control head when removing it for an aftermarket head unit, so if you've done wiring for that you may have inadvertently placed a dependency on the receiver for power ?
Getting into a bit more detail of when the prob started and what was done during that time will help. The FSM may explain it also if you trace the connections. Using the correct terminology from the FSM also helps keep everyone on the same page.
CDM = Control Data Module
I have a FSM for MY 94 but not for the 92 that I'm working on. It is the CDM it's under the passenger side dash and I just left it in place since I couldn't figure out what it was still needed for after the Bose was removed. I have wired in the resistors for the dimmer circuit and get no sys or codes but I am not even sure that was needed since the car is also a C68 car and many report not needing them in that case.
So the CDM stays and I have no idea why but since removing causes the car not to start and the dash to lose power it's a no brainer at this point. I've done all the inverted head in footwell work that I'm going to do for a long time.
Last edited by 94z07fx3; Jan 5, 2013 at 01:04 PM.
Advanced
Joined: Apr 2019
Posts: 57
Likes: 5
From: Supply, NC
Removing Bose tuner box
Hey guys, I am installing a stand alone sound system in my 1990 ZR-1, I just removed the tuner box and can report the car starts and runs as it should, not sure about any DIC lights yet.
Le Mans Master
Joined: Sep 2013
Posts: 6,192
Likes: 750
From: near the thumb in the mitten
Reviving the dead. The thread is from 2013. There a a couple things with removing Bose system. It's a component system tuner in dash. Reciever\ radio mounted remotely with amps built in to speakers. To change radio you will need to run new wires or make jumper harness to Reciever to use factory speaker wiring and p/antenna. You will also have to run a jumper coax from new radio to coax at Reciever. Book 1 FSM sections 9A information related to radio and 8C for dash disassembly. Book 2 FSM section 8A wiring diagram. There is a TSB to add resistor for lighting error code.
Advanced
Joined: Apr 2019
Posts: 57
Likes: 5
From: Supply, NC
Cdm/radio tuner removal
I completely removed all the Bose components. Started the car seemed to run fine, aftermarket stereo in functioning properly. The 70-1858 wiring harness does not plug into this cars wiring. I had to wire it all.
Do any of you guys know which wire needs resistor to kill SYS light. It did not come on yesterday when I started the car although I already had service engine light due to vacuum and 02 sensor, thanks for the replies.
Do any of you guys know which wire needs resistor to kill SYS light. It did not come on yesterday when I started the car although I already had service engine light due to vacuum and 02 sensor, thanks for the replies.
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