Hi all:

I own a 91 Sedan deVille with 96k miles.

Recently the FDC (Fuel Data Center) and the ECC (Electronic Climate Control) went totally blank, no c or d error codes either. Also the heater blower will not come on. After reading many threads on this subject I have come to suspect either the Body control module or the power supply but to be honest I'm still more confused than a baby in a topless bar. :)

I've read that on this particular year and model the power supply is internal on the BCM but I'm not quite sure. So I'm wondering if this is true and I buy a new BCM would a new power supply also come with it? (would save the trouble of deciding whether or not it was one or the other that's gone bad)

Also I've heard that the prom needs to be swapped from the old BCM to the new one. I understand that this has to do with the odometer information. My question on this is if I have a mechanical speedometer and odometer would this have to be done?

Any help on this would be greatly appreciated,
thanks!
Cujo

Just an update to my previous post, if anyone can benefit from my mistakes It just might make me feel a little better. :)

After reading all the threads on this subject I decided to replace the BCM. Once I had the new one installed I found no change in condition. major bummer! The next thing I did was to remove the trim arouind the instrument cluster revealing two screws which held the FDC in place, I removed these, slid the FDC forward and unplugged the harness from the back of it. I then restarted the car. Bingo! The ECC came on all lights displayed, blower kicked in and all was right with the world.

So now I'm assuming that the circuit board for the FDC is FUBAR. I brought the unit in the house and dismantled it and removed the two capacitors from the circuit board. After testing both capacitors I found one that wasn't discharging correctly. The reason I suspected the capacitors was from a previous post I found in this forum. Tomorrow I will track down the capacitors and replace them both. If that doesn't work I'll just bite the bullet and replace the circuit board for the FDC.

I'll post again as soon as I've replaced the capacitors and let everyone know the outcome. I'm still embarrassed about replacing the BCM and thought about leaving that part out of this post. lol, but if anyone can learn from my mistake it will be worth it.

Cujo

Finally got it fixed!

As I stated in my previous post I suspected the problem was in the FDC circuit board. Well I was right about that but not in the way that I thought.
After replacing the capacitors on the circuit board of the FDC I had the same condition. In fact when I would plug it back into the harness it would smoke. Rut Roh! So back in the house again for disasembly. :( At this point I'm very discouraged and disapointed. I started to look more closely at the circuit board and noticed that where the harness plugs into the board one of the connectors didn't have any scratch marks on it like the others did. It didn't seem to go anywhere on the circuit board either so I assumed it was a ground. I went back out to the car and with a test light I pushed on the top and bottom of each connector on the harness pinching them together better to hopefully get better contact with the circuit board. I avoided the connector that was hot. (didn't want to short anything out) I plugged the FDC back into the harness, (yippee! no smoke lol) started the car and by some small miracle everything worked. phew!

After all was said and done I believe the problem was in the connection between the harness and the FDC circuit board all along. If you unplug the harness from the FDC with the locking tab facing up the ground will be the first connector on the left. Hope this helps someone out there. :)

As a side note I called the local Cadillac dealer about the capacitors, their response was they did not carry them and that their procedure was to send the circuit board out for repairs. I asked how much and they said $500.00 I almost fell out of my chair! They are definitly off my Xmas card list. Also if you can't find FDC or ECC's at the salvage yard Carquest carries these parts. Not cheap but a heck of a lot better than those ripoff artists at the dealer.
Cujo