Any time you notice gremlins in the electronics, first check the battery cables for corrosion. Also be sure the battery voltage is not too low.

 

I've had a 90 DeVille for 2 years and the fuel data center has done the exact same thing from a year before i bought it from my mother. the data that it contstantly flashes is accurate as hell. I've had it checked and noone can find any reason for it, no other problems in wiring or anything, I've just learned to live with it.

 

:welcome:
Welcome to the Esteemed Caddycommunity!

If it's not a problem consistent with Ranger's
excellent trouble shooting diagnosis; I'd say
there's a ghost in the machine. You might
want to turn the display off so that it doesn't
irritate you, or alternatively call Ghostbusters.

Best Regards :cheers: :cheers: ,

TomDeville
:coolgleam

 

You know for the most part it does not bother me. So I guess I will probably just live with it for now. When I come into a bunch of money then I may have Cadillac replace the unit but for now I have a strobe light.

 

:wave: Nothing to add to the subject but to say from your ID your in Tulsa, I'm in Broken Arrow.. Hi! Neighbor!

 

Same thing happens with my 91' Deville. Now I have a problem with a letter "d" displayed in my gallons left location. I have posted to try and find out what is going on.

 

EX20-

the "d" showing up in the fuel data center display is indicative of a data line failure between the the BCM (body control module) or PCM (powertrain control module) and the fuel data center (FDC).

Data for the FDC is sent by the BCM and PCM to the FDC where it is then displayed. When you see a "d" there, it means loss of [d]ata. Sometimes you may also see a "c" which I beleive means loss of [c]lock, as the timing of the serial data line is controlled by the PCM/BCM and a bad module may not transmit or maintain the correct timing & "carrier" signal between two points on the network.

The following items may be repsonsible for these problems:

1. bad battery connections or weak battery
2. bad grounds
3. faulty wiring between modules
4. faulty, damaged or poorly seated connectors at modules
5. internal module malfunctions that may or may not be related to wiring issues.

So, tracking the cause of this down can be a project. Sometimes this will affect the climate control center also. where a "c" or "d" will show in that display as well.

Hopefully this gives you someplace to start.

Kevin

 

I have the same problem with my '91 deville. I've been trying to find out where the BCM and PCM are located EXACTLY, Any ideas????

 

umbis-

91 SDV, PCM is located up behind dash board on passenger side. Probably easiest to get at it by dismounting the glovebox assembly. 90 is nearly identical AFAIK. BCM, right now it escapes me where they tucked this away. Methinks it is up in the dash somewhere also (maybe on top, under the dash pad) or maybe I'm confusing the two (and the BCM is behind the glovebox).

Right now, I can't remember for sure (got rid of my 91 over a year ago when it started to eat me alive in repair costs) and my 95 is much different in how the modules and such or layed out. My mom had a 90 - since traded for a 97 - but I never did much work on it. It was actullay a very reliable car, more so than my 91; well at least for the last few months I owned it.

Kevin

 

Yay! I was just getting ready to post a similar question. The fuel data center and climate control center in my '89 Deville both display a "C". It will not enter diagnostic mode. Worse yet, it consistently blows hot air out of the window defroster and floor heater. Not an ideal situation when it's 92 degrees outside.

I am by no stretch of the imagination a mechanic, but I'll take these suggestions and see what I can find...or to my mechanic.

Thanks for the info:bouncy:

 

Yup,

no access to on-board diag's when the FDC and climate control are not "on the line", since they serve as the user interface for the whole system. Until you can get these back on the communications network within the car, you cannot enter diagnostics.

Also, in regards to the funky climate control settings - this is the "fallback" mode that is automatically selected in the event of a climate control panel failure. Really nothing can be done about this either unitl the control panels are returned to normal operation.

Kind of a catch 22, since you have a problem but can't use OBD to diagnose since you can't get access to it.

Best of luck!

Kevin

 

I think i may have found the solution to all of your porblems. My father has an 89 cadillac deville and recently his dash board has been doing the same exact thing. I found that inside the body control module, (located behind the glove box) there is a prom under the little cover held on by three screws. If you remove the prom and clean the contacts in the socket, your problems should go away. If you can't clean the contacts then rockauto.com has the socket itself on there website. You will just have to do some soldering. Hope this helps everyone.

 

Well, I finally decided to do something about the letter "d" in the FDC display. I also had the erratic FDC display problem when it did finally start showing numbers.

It turned out to be the BCM. Got a remanufactured unit from Rock Auto and it works fine.

The location on my 1991 Sedan Deville is behind the glovebox. It is towards the top left side of the glovebox opening. It is in the horizontal position, NOT vertically on the firewall.

Good luck!

 

khazmcdust will probabally never get to read this but thank you man you solved my problem i took off the bcm cover poped off the lil chip thing and brushed with wire brush an walaaa my temp and gas gage work like a charm saved me around 100 dollars thank you again man your are a genius. IF YOIU HAVE THIS PROBLEM READ UP A COUPLE COMMENTS AND IT WILL WORK LISTEN TO ME!!!

 

IT WORKS GUYS A GENUIS!!! THX SOOO MUCH MAN YOU ****IN ROCK.I BOUGHT MY CADDY FOR 300 BUCKS CAUSE THE GUY COULDNT FIGURE OUT WHAT WAS WRONG.. AH HUM GAS AND TEMP Gauge showing d and blowing air when the car wasnt on.. then did what khazmcdust suggested ans boom shaka laka it works fine thx again man!!