I hope someone here can help with this, I am clueless here. I have a 1993 Cadillac DeVille. I had a couple days where the dash indicator lights were coming on at random, for no apparent reason. At this time, when I start the car, the air conditioning comes on and will not shut off. There is a "c" displayed in the fuel gauge area. I can't read the codes by using the buttons on the climate control, it is not responding.
What is the car trying to tell me?
Thanks for any information.

Man, this sounds like something is really screwed up. Can you be more specific as to *which* lights are coming on at random? Is it isolated to the right or left information center? Is it isolated to the left or right of the speedo?

I don't really know where to start. Might start by checking the voltage of the battery by using a voltmeter. Should be between 12 and 14 volts.

Crawl underneath the dash, remove all the hugh panels and see if you see anything shorted, disconnected, etc.

The BCM is located behind the dash on the passenger's side. Remove the glove box to gain access to it. Check the connections to it.

The PCM is located near the BCM. My FSM for the 93 Deville does not indicate exactly where it is at. It says only that it is located under the instrument panel on the passenger side. Check to make sure the connections to the PCM are ok.

Does the car run normally otherwise? Does the speedo work?

What you may want to do is crawl underneath the driver's side of the dash and make sure all the connections to the displays are ok. There are several connections you should check:

- Dash wiring harness - check for damage
- digital instrument cluster connector (if you have the digital cluster)
- information center connector
- dash harness internconnect
- instrument cluster connector
- fuel data center connector

If there's any time an FSM would be handy, this is it. If you can't solve the problem by inspection, you might consider getting one. I'm looking at mine for the 93 Deville and this is something that could be very useful to you.

Thanks for the reply!
There is a small "c" in the fuel area and the climate control area.
The battery checks out ok and the grounds also. The car is running ok and the speedometer is working.
I have only the Haynes book, and it doesn't go into enough detail for this. I have looked everywhere I can think and have never seen reference to the "c"'s showing on the readout. Any idea what that means??
Will continue to check for any loose connections, but have not found any so far.

The "c" means the display has lost the clock signal from the BCM. Both displays doing it at the same time sounds like a new BCM may be in your future. Check the wiring and connections first though.

http://www.cadillacforums.com/forums/attachments/electrical-technical-information/13422d1126157320-fuel-data-center-wiring-93-deville-41840360.gif

I'd have to agree with Dave. I'd check the connections anywhere you can. Also check all the wiring harnesses for damage (e.g. nicks, shorts).

Might also be useful to reseat the connectors on the BCM.

If the engine is running fine, I would leave the PCM alone so as to not cause another problem.

There are a sufficient number of 93 Devilles in junkyards, you should be able to get a replacement BCM readily and for cheap. Many junkyards will let you bring it back if swapping it doesn't help your case. Also, they'll put a little warranty on it. I find that many junkyards will also pull them for you.

Wow, thanks for the info, could not get a straight answer anywhere until now!
Will be working on checking connections, wires, etc over the weekend, and take it from there. I'll let you know what I find out. Thanks again!:grouphug:

Were you able to fix the problem?

Sorry for the delay in response, had to go out of town.
Well, problems persist. I can't find any loose connections or bad spots anywhere that I can see. I replaced the battery.
At this point, I have a "c" in the fuel area and a "c" in the data center area. There is a "service engine soon" light on. I am unable to read the codes, the data area is unresponsive using the climate control buttons. Is there any other way to read or clear the codes?
The car seems to be in a "learning" mode now, it runs, but then will idle rough for a while or run at a very high idle.
I am at my wits end.
I also had a problem with the trunk pulldown not working. When I replaced the battery, the trunk shut. :bigroll: It worked a few times and now is not working again. I doubt the computer problem is related to that, but I am mentioning it just in case.
Any help appreciated.

What if you took your car to Sears and let them to an electrical diagnosis on the charging/battery system? Maybe your alternator is shot. Maybe it's putting out a huge voltage. Did you check the voltage?

BTW, Helm is having a 50% off sale on their 1990-2000 FSMs. If there's a time to get one, now is it.

oh, geeez, this is like a needle in a haystack (showing my northern roots), I'll try having that checked out.
Thought the battery was good, was only a couple years old, but all of a sudden it went down. I have since learned that the high heat here in s. Fla wreaks havoc with batteries and sometimes electrical..:bigroll: :mad:
Not much I can do about that.
Thanks for the suggestion, I'll get that checked out. I wish it could be as simple as the alternator.

I had a problem with my '85 Deville where I was going through batteries quite often. Turns out that it was a bad alternator that was charging at too high a voltage, cooking the battery. Got that fixed and the problem went away forever.

The wiring that runs to the alternator and ISC will have a wire with a green connector head. Make sure that this is not making contact with any metal. This will render the alternator ineffective. This wire is only used when resetting the ISC minimum/maximum idle at least that I am aware of. I read something along the lines of a bad BCM too. Since you are basically working blind on this problem and the money that could be involved. I would try going to a salvage yard. If the key is present remove the battery you already own put it in the junk car. Check to make sure the BCM in this car is not malfunctioning. If it is okay buy it and put it in yours. This will at least rule out that problem and is cheaper then dealership experiments.

I think the bases have been fairly well covered here, but another thing worth the small investment is a continuity/circuit tester. If you can get your paws on the FSM/electrical diagrams, you'll be able to see which wires you should be able to get continuity on going to the BCM & PCM...and if the wires complete a circuit, and there isn't continuity, you know there's a problem with the wiring (or perhaps a sensor between in some cases) in that circuit. There are a lot of tests in the FSM for jumpering and the like too...the manual is well worth it...but this particular test will require some paitence :rolleyes: