89 cadillac sedan deville 4.5engine 174k+

Drove the car today..all was well. Went to leave for work and upon starting the blower motor turned itself on full blast...and the a/c display and also the fuel guage dispaly both have a "c" character only showing. I also now have a SES light. Pushing any buttons does not help. The blower will not shut off...and the disalys will not change. Car seems to be skipping now mabye. I will work on it in the morning...but does anyone have a place for me to start? does the "c" mean anything?

thanks for any advice. Even if i should post this else wheres for more views please let me know. thanks

Small update. Didnt have time to look for grounds or bcm today but i did unhook and clean the battery and terminals. they were clean as can be. The SES light goes on and off now...it varies..but the car runs fine and now the 2 displays alternate between "c" and "d" lol :crying2:

More than likely the problem is the BCM. I a had similar problem in my 89 DeVille a while back and it turned out to be the BCM.

thanks for the reply.
Did you have either of the letters showing on your dispalys? Im wondering if there is a way to test this part before i purchase a new new. Im sure if i put a new one in...and it didnt work i would then have to trace down the grounds.

I located the bcm i think today. 2purple connectors in the glove box and it was sideways. Held in by 2nuts ...i broke that plastic where it is attached...damn thing wouldnt come out.

Could you tell me if this is definaly the bcm? it has a number on it 1228784. gmparts direct shows it as a ecm though and it see a compartement in it that looks like a eprom. Only 1 junk yard around has one..and they dont know either if its the bcm or ecm but they want 75bux for it and wont test it or warantee it. a referb from rock auto is 85 plus core....i dunno what to do :helpless:

I was looking at an 89 DeVille (for sale) on the weekend, Exactly the same problem. The problem scared me away, I would go back to buy if it is an easy fix.
Please post the cure when you find it.

Thanks

I located the bcm i think today. 2purple connectors in the glove box and it was sideways. Held in by 2nuts ...i broke that plastic where it is attached...damn thing wouldnt come out.

Could you tell me if this is definaly the bcm? it has a number on it 1228784. gmparts direct shows it as a ecm though and it see a compartement in it that looks like a eprom. Only 1 junk yard around has one..and they dont know either if its the bcm or ecm but they want 75bux for it and wont test it or warantee it. a referb from rock auto is 85 plus core....i dunno what to do :helpless:

I am sorry I can't help you too much because the BCM problem was diagnosed by the Cadillac dealer and they replaced that computer for about $400. This was a while back, about 5 or 6 years ago.

But the problems you are having are just about the same as the ones I was having with my 89 Sedan DeVille; funny letters in the fuel data pannel, etc.

Ordering a bcm from rockauto now. its gonna take 2 weeks :annoyed:

Got it in. Works great. Good as new. Ended up getting it from GMparts direct.

Got it in. Works great. Good as new. Ended up getting it from GMparts direct.

Question.
I had the same problem with my '89 Deville, but it was showing a "d" instead.
Now I replaced the BCM with a used part off of ebay and now it showing a "c" instead. So my question is when you first fired it up did it immediately solve the problem or was there some sort of waiting period, maybe for it to adjust?

I'm trying to see if I received a faulty BCM.

-Allen

Question.
I had the same problem with my '89 Deville, but it was showing a "d" instead.
Now I replaced the BCM with a used part off of ebay and now it showing a "c" instead. So my question is when you first fired it up did it immediately solve the problem or was there some sort of waiting period, maybe for it to adjust?

I'm trying to see if I received a faulty BCM.

-Allen

Swapped the new PROM into my old BCM and everything works fine.
Thanks.