Cadillac Repair: 91 cadillac brougham - 3 digit trouble codes, climate control system, cadillac brougham

Question
QUESTION: Hi,

I've looked through the past posts, however didn't see an answer to a question like this. I have a 91 brougham that's been running rough at idle, and surging while driving. I got some pretty severe spark knock and/or detonation the other night and have had it parked since.

The kicker is, it used the climate control system to check to codes, and I only get a three digit number code? The codes it displays are 132, and 140. It was showing 148 and 150 however those are gone after clearing the codes, although I haven't driven it since. These are all followed by the Celsius symbol.

Problem is, I look online and I find that all those codes are invalid without a "letter" designation in front of them, and there is none. In the segment display check, there is only a '-' (minus) symbol in front of those three digits in the display...?! Is there something different about how to read codes on a 91 brougham and if so, what's the procedure?

Any ideas? Thanks very much in advance, as this is driving me nuts.

Thanks again,

Steve

ANSWER: it is possible that the 1 that you are seeing in front of the 32 and 40 is supposed to be an E but some of the segments are burnt out on the display.

Try checking for codes and when you first push and hold the OFF and WARMER buttons, All of the digits on the display should illuminate and you should see 888 for the digits unless some of the segments that make up the first 8 are burnt out.

If this IS the case, You will have to replace the complete climate control panel.

---------- FOLLOW-UP ----------

QUESTION: Thanks very much for your response. When I push the OFF and WARMER buttons, the segment check display comes up exactly as "-188". I can see the lighted segments (when off and unlit) through the plastic in front of the display however and that's all that is there, no third 8, as in "-888" only a "1" is present in that first position, not because it is burnt out, but because that's the only segment in that position.

Did Cadillac ever use this kind of display on this model, or is something else amiss? I should have mentioned that this 91 brougham is also a limo, so therefore was most likely the "coach builder" or "armored" option for that year. Would this make a difference? There is also a standard OBD-I diagnostic plug directly below the climate control system. Would it be worth purchasing an OBD-I reader and attempting to get the codes that way?

I have a 93 Chevy Corsica which has a plug like this, and by simply bridging the top and bottom connectors on the right hand side, the codes are displayed through the "check engine" light. Is there a similar trick for this Cad that would save me the $ of buying an antiquated code reader?

Thanks again for your help, I greatly appreciate it.

Steve

Answer
These directives are for a 1991 NOT a 1981 Brougham Rear wheel drive with a 5.0 or 5.7 engine..

My apologies, See what happens when you get old.

There is a diagnostic connector under the dash.

It appears as this

FEDCBA
GHJKLM

You have to jumper A (Black with a white stripe wire) to B (white with a black stripe wire) together and count the light flashes of the check engine light.