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1997 DeVille
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9 Posts
Discussion Starter #1
I have a '97 DeVille which has developed an odd and potentially deadly problem. Sometimes on hard acceleration the drivers seat begins moving me forward into the steering column and won't stop until it reaches the full forward position. I can't override the movement with the seat control switch. This is very unsettling because I'm 6' and it compresses my legs under the steering column. When this happens it is usually at the worst possible moment, when I'm merging into heavy traffic. The car has 114k on the odometer. The drivers side rear window also stopped working from the driver's console but can still be put up and down from the rear door switch. The window stopped working when I plugged my new GPS unit into the cigarette lighter one day. 24 hours later the window quit working. The turn signals also occasionally stop working in mid click for no apparent reason. If I didn't know better I'd say the car was haunted. I suspect a computer software error and want to reboot the CPU so the firmware reloads a fresh copy (a friend suggested this) but I don't know the protocol. Any ideas anyone? I really like the car and would hate to have to junk it because of this.
 

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1990 DeVille
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181 Posts
I think it's a simple short, and it's probably at the control assembly. Pull the switch panel and inspect carefully. If you see anything (foreign material, bent conductors, etc.) fix it. If not, consider replacing it from pick 'n pull.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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71,046 Posts
BillDK, Go to the top of the main Deville page and read the sticky thread titled "How to pull codes". Read up on how to retrieve your car's Diagnostic Trouble Codes (DTC) from the built-in system. You want the OBD-II link and procedure. A couple of practices and you'll find out if the car or a module have set fault codes. Write them all down, and whether they are Current or History. Don't clear the codes when asked by the instrument panel - just turn the key off for 30 seconds and exit the diagnostic.

C'mon back - and :highfive: ........ :welcome:
 

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deville
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41 Posts
bud sounds like you got a short somewhere?it does sound like the switch is shorting out.also check to see if theres a relay that controls memory seat...have you installed recently any electrical stuff like alarm ,radio,etc,cause sometimes goofy installers take any power wire they find.if you cant resolve at least see if you can unplug switch before your car does kill you...good luck.
 

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1997 DeVille
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9 Posts
Discussion Starter #5
Thanks, friends. I've looked at the codes several times but there's nothing visible. I will go back and maybe there's something I missed. I've not touched the car aside from using a Pharos GPS unit from Dell which I plugged into the cigarette lighter on the door whose window immediately stopped working from the command console. I kept the GPS under the drivers seat for awhile and while it was plugged in the seat used to act up by moving forward on its own. I took the GPS out of the car thinking that would stop it but it didn't. The turn signals also now quit after being on for about 5 seconds. Flicking the stalk causes them to come on again for about 5 seconds and then they fail. I'm starting to think about driving my old TR4 (pre computer days) but summer in Florida is brutal.
 

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1993 DeVille 4.9L
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21 Posts
remove the negative cable, wait a little bit then put it back on, then follow the procedure for restarting the electric system.
thats how you 'reboot' the system
 

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1997 DeVille
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9 Posts
Discussion Starter #8
I did try removing the cable and let the car sit for a week while out of town. That didn't fix anything.

I did accidentally fix the problem, however. It turned out it was a short, but not where you would have expected it. The turn signal relay was defective, causing the turn signals to work for about 5 seconds before quitting. Apparently when the throttle was wide open and I put the left turn signal on to merge the combination of signals caused the computer to be tricked into thinking the seat should go forward. I replaced the $13 part and the car's worked perfectly since.

Now if I can just figure out how to fix the back window on the driver's side I'll be a happy camper!
 

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1995 SEDAN DEVILLE-4.9 & 1978 SEDAN DEVILLE-425
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1,673 Posts
I did try removing the cable and let the car sit for a week while out of town. That didn't fix anything.

I did accidentally fix the problem, however. It turned out it was a short, but not where you would have expected it. The turn signal relay was defective, causing the turn signals to work for about 5 seconds before quitting. Apparently when the throttle was wide open and I put the left turn signal on to merge the combination of signals caused the computer to be tricked into thinking the seat should go forward. I replaced the $13 part and the car's worked perfectly since.

Now if I can just figure out how to fix the back window on the driver's side I'll be a happy camper!
Glad you found the fix before anything really bad happened-----being compressed against the steering wheel/column while driving must have been a real bitch---not to mention the knees into the dash!
 

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1997 DeVille
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9 Posts
Discussion Starter #10
The worst part was that it would do it on the on ramp to the interstate under heavy acceleration when trying to merge into high speed traffic (going 75 mph). Folks in Tampa like to drive fast. Imagine trying that at night in heavy rain and having the seat decide to go into crush mode and you can imagine you'd get a little rattled. I'm 6' tall so there's not much room under the dash. Frankly I'm really happy it's fixed. I never want to go through that again.
 

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1997 DeVille
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9 Posts
Discussion Starter #11
Ok, here's the last word on the killer DeVille....

IT DID TURN OUT TO BE THE PORTABLE GPS THAT CAUSED THE PROBLEM!!!

I took it on a trip of 90 miles with the GPS on (but not plugged into the lighter). I turned the car off and took the device off the windshield to stow it under my seat. My seat started moving forward automatically. I moved the GPS away and it stopped. I put the GPS back under the seat and the seat moved forward again. Finally, I tried putting it in the glove box and my seat began moving forward again on its own. Apparently the GPS puts off so much RF that it gets picked up by the wiring harness and relayed to the computer where the noise is interpreted as a move seat command. This puppy is bad news...

Just a fair warning to you, if you own a '97 DeVille, don't buy a Pharos portable GPS sold through Dell electronics. Or if you do, prepare for the ride of your life!!!
 

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04 Deville, 11 DTS Premium, 00 Deville (sold), 02 Deville (sold)
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2,688 Posts
Apparently the GPS puts off so much RF that it gets picked up by the wiring harness and relayed to the computer where the noise is interpreted as a move seat command. This puppy is bad news...
Wow.... That one of the worst cases of EMI (Electromagnetic Interference) that I've heard of.

Just a fair warning to you, if you own a '97 DeVille, don't buy a Pharos portable GPS sold through Dell electronics. Or if you do, prepare for the ride of your life!!!
Do you think I could borrow that GPS to put in my wife's car? :lildevil:
 

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1997 DeVille
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9 Posts
Discussion Starter #13
http://www.cadillacforums.com/forums/images/smilies/tsk.gif

Oh, I'd better pass on responding to that one! Big trouble there!
I think the problem stems from the fact that the GPS goes into a quiet state before shutting down entirely probably about an hour later. That way it is available in case you want quick access. The caddy also keeps the accessory power on when you shut off the car so you can move seats, listen to music, etc. Apparently the intersection of the two device characteristics is that you have a EMI getting generated at the worst possible time and the DeVille's computer picks it up as soon as you're putting it under the seat or in the glove box. It's like the car is haunted.
 

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1997 DeVille
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9 Posts
Discussion Starter #14
One final word on the caddie seat issue. It looks like the seat position sensor was feeding false readings to the seat position controller. This was probably due to the fact that they used potentiometers as sensors for the seat position. As the potentiometer gets dirt inside it gets noisy and the signal gets erratic. It also makes the sensor input more variable and likely to assume the seat is in an incorrect position. It's probably a dirty potentiometer that's causing all this...
 
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