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1968 Cadillac Sedan deVille, 1994 Chevrolet G20
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Your not the only one here with this problem. Try reseating the connectors to your ECM/BCM.
 

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Hiya Chuck -

I have a similar problem as you and was wondering if you had found a solution. I think it might be the BCM, but I cannot be sure. Even the Caddy dealers can't be sure. I don't want to replace a $200.00 part unless it is indeed the problem. I have to believe that this problem has been solved before since it appears to happen on various models and years of Caddy's. Mines an '89 DeVille

Bill
 

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Hey Bill-
I have discovered that the BCM connects into the ECM so there is no telling what? There was one guy who told me to reseat the connectors on the ECM\BCM so I'm gonna give it a shot.
 

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Hiya Chuck -

Yes indeed the BCM and ECM are connected. The communication line between them is even monitored... such that if there is a fault there, the "Ckeck Engine" light will illuminate and a code will be displayed on the Electronic Climate Control (after the OFF and WARM buttons are depressed, etc, etc, etc.). Since it is the BCM that controls all of the inside (or body) functions of the car (including the ECC, Fuel Display and Stereo) I am assuming that it is indeed my BCM that has S*** the bed. However, before I go and purchase one, I will try reseating the connectors as Dave had suggested in an earlier post. i may even try this tomorrow... I will psot results if I do.

However, there is one real hesitation that I have about changing the BCM though... since the BCM is a highly sophisticated electrical componant (computer) that is fed by and, in turn, feeds multiple other electrical componants, it is highly possible that one of these "other" componants have gone bad (such as a short to ground or excessive current draw), and perhaps by doing so also causes the BCM to go bad. If indeed this is the case, then by changing just the BCM without finding the root cause for its demise, I may just fry the new one I put in as soon as I power it or the car up. At over $200 this is not an chance I really would like to take. But... on the other hand... I am freezing my butt off each day Idrive the car... it may be worth it

Thoughts?
Bill
 

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Wasn't able to get to it yesterday, but today i pulled both the BCM and ECM and re-seated all of the connections on both units. Also took the covers off of the prom chips to see if I can see anything that might be bad... no burnt components in either. Put them both back. Same problem... "c" then "d"... Looked up the cost of a new BCM... $110 from gmparts.com. Junkyards want $50-80 ....

Anyone else have any clues?
 

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I'd like to bring this back to the top. This issue does not seem locked to my particular model and/or year of Caddy. Someone out there must have run into this before and found a solution... please help
 

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I'll make it a Sticky for you. I'm sorry I can't be of more help, but I'm stumped.
 

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da_bills2 said:
I'd like to bring this back to the top. This issue does not seem locked to my particular model and/or year of Caddy. Someone out there must have run into this bef:banghead: ore and found a solution... please help
Hi

Have the same problem going on
no heat ,blower on high,dash lights on BRIGHT,

The factory service guide for cadillac mechanics says
if both panels display d only replace the bcm....d on diplay panel represents a loss of data signal
a c on the display panel is a loss of clock signal the factory tech reference goes on to say if both panels are affected several circuits need to be looked at
if deppressing the off button on the ecc does not shut of the blower motor
the panels are not in communication with the BCM.

I am going to replace the BCM which is $75.00 plus core
From B.and B auto parts
But i will investigate the site someone else on the sight recommended on this forum site.

Hope i gave ya a little more info
but i too have been banging my head too too cold in WI to be running around with next to no heat .
Hopefully some one out there has had the same problem and will be kind enough to pass on the SURE FIX FOR THE Problem
GOOD LUCK
HAPPY HOLIDAYS TO EVERYONE
Don @ katdons 3labs
 

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All -

Thank you all for all of your help (and thanks to Dave for making this a sticky). I have not yet changed my BCM, but its getting cold here in Western NY as well. Maybe I'll just have to give in...

Two questions though:

1) When you speak of "several circuits need to be looked at" exactly what circuts are you referring to (was the tech specific in the circuts?)

2) If you do buy a new BCM from B.and B. I am assuming that you will have to move your prom chip from your BCM to the new BCM... correct? (Also who is B and B???? $75 is an awesome price for a new BCM)


Again Thanks All
Bill
 

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da_bills2 said:
All -

Thank you all for all of your help (and thanks to Dave for making this a sticky). I have not yet changed my BCM, but its getting cold here in Western NY as well. Maybe I'll just have to give in...

Two questions though:

1) When you speak of "several circuits need to be looked at" exactly what circuts are you referring to (was the tech specific in the circuts?)

2) If you do buy a new BCM from B.and B. I am assuming that you will have to move your prom chip from your BCM to the new BCM... correct? (Also who is B and B???? $75 is an awesome price for a new BCM)


Again Thanks All

Bill
Bill

First off Bill I have a 92 Deville with the 4.9 pfi engine .
The factory service manual i have says for 1992 and 1993 Devilles
so i cannot be exactly sure the info i can give you will pertain to you`r 1989
Deville SO....

here is the circuit description that pertains to 92 and 93 Devilles.

The Bcm supplies the FDC and ECC with certain info.
Through ckt 719 the BCM sends data to the FDC.
Through ckt 705 the bcm supplies the fdc and ecc with a 5 volts reference.
Through ckt 751 the BCM supplies a reference ground.
A clock signal is provided to the fdc and ecc over ckt 713.
The Bcm supplies a 16 volts source to the ecc and the fdc through ckt 716
Through ckt 718 the BCM sends data to the ecc.

Also Bill if you depress the off button on the ecc does not result in the blower motor turning off then,the panels are not in communication with the Bcm.

This could be caused by a loss of 5 volts or ground to the panels. this would be ckt 705 5 volts ,letter (T) on the connector, which is a tan colored wire on ecc connector which goes to c13 pin on the BCM. 5 volts

For the display panel diagnosis for the 92 and 93 Devilles
the trouble shooting chart says
If BOTH panels display (d) replace the BCM.
Oh ya, this is for FYI when you get you`r new BCM MAKE SURE you are touching a known GOOD GROUND on your car with your hand as you remove new computer from the box with the other hand,and yes ya have to R&R the prom.

Bill,
That parts house is in New York (BBautoparts.com) found them surfin

They gave a price for the 1992 Deville BCM at $75.00 plus tax,but you need to give them the numbers on the old BCM to make sure ya get the correct computor also, at that price it has to be an after market elec part but i`d rather buy after market than pay a 300%mark up at the caddy dealer. There is a $95.00 core charge and $10.00 for shipping
or $20.00 for over night.

Don
 

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<ponders aloud> I wonder if Wes added this to his FAQ yet, so I can unstick this thread...
 

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No...not yet. Still have not gotten my BCM.... :( Fortunately it turned warm here in NY (50+ yesterday)... so I'm not too concerned... yet ;)
Will post results when I replace it
 

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I have exactly the same problems here with a fleetwood '90.

Is anyone from Europe or even Germany and could give me a hint where to get the BCM and ECM? No results with google ...

Because shipping from US is around 120$ ... :rolleyes:

V8fan
 

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Hi! I have a 1989 Sedan DeVille and just recently was having the same problem, only mine said 'c' and then sometimes 'd'. I was unable to tell how much gas I had and my blower was like stuck on super high...freezing cold air!! I switched the BCM (Body Control(computer) Module) for another one from a junkyard and my problem went away!!! In my DeVille the BCM is located behind the glove box, maybe it's in the same place in your Fleetwood. I got lucky and only paid $10.00 for mine but the average price used is around $50.00 or new about $239.00 (OUCH!). Goodluck...I hope this helps. :)
 

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Thanks guys for posting back with your solutions ( v8fan; mbrakeall). Letting us know the solution to this annoying and expensive problem will no doubt save someone time and money and aggravation. It's a shame that several of the original poster's with the problem chose not to return and let us know how they made out. If the results of the research and solutions are not posted back by the people that ask the question, then the thread frequently fails and people that come to find an answer to their problem can't find out what works, so thank you for posting back
 
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