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Bad BCM/Bad Ground?

3714 Views 4 Replies 4 Participants Last post by  ewill3rd
I got a 1993 STS, and once or twice a day, the digital display under the spedo and tach will say Service Ride Control and Traction Disabled, the the fuel economy display will go blank and just have little lines. Then the entire climate control display will do the same thing and just have lines and then it will go to Defrost at 75 degrees on auto, and none of the bottons will work. After about 10 minutes, everything will go back to the way it was. The car will run fine and no lights will come on. The codes I get are IO32, IO33, IO34, IO37 and IO39. Any help is appreciated, this is driving me crazy. Is the BCM bad or maybe just has a bad ground somewhere or a loose connector??? Thanks.
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I have a simular problem. I've heard a low voltage in the charging system / low battery...... But........ It may just be the plug for the display?

I use an electrical component and something on the dash goes wacky.

I sometimes start my '93 STS and the speedo goes to 140, along with other momentary glitches. Sometimes my radio cuts out & my gas average changes to instant avg.

Sometimes when I just get going, the dash & ignition cuts in -n- out , but just as a glitch..... it all resets it' self. ..Then drives fine. ...Sometimes using the power window sets it off for a 'tick'.... Then it's fine.

I talked to a Cadillac guy, and the connector to the dash is going bad. He suggested to put up with the annoyance, or spend big bucks replacing the display.

I chose the cheaper choice.
Mountie is correct. These cars do not tolerate low voltage or bad connections. Check the battery connection and have the battery test for starters. Rule out the obvious, easy and cheap first.
Does this also affect the IPC display or warning indicators?
It sounds to me like a loss of communication.

That older car will use a UART data bus, which is a nightmare to diagnose.
There were bulletins years ago to start replacing modules in a certain order for complaints like that. You can run into thousands of dollars chasing it if it what I think it could be.

They can be hard to diagnose but what happens is one of the modules quits toggling the voltage on the data bus and it just holds the voltage high or low, all modules lose communication with eachother and they default to a pre-programmed fail safe mode but you lose most of your display information and a bunch of lights come on.

The most common failure on those, even though it is way down the list, is the HVAC programmer located behind the glove box.
I have seen other modules fail in the same fashion, but if you have to roll the dice, I'd start there.
After that it gets hard!

Good luck.
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Oh... but yeah, first you should make sure your electrical system is in good shape, clean and tight connections at the battery and block.
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