Bad BCM OR Electrical problem?

2004 CADILLAC DEVILLE
4.6L • V8 • FWD • AUTOMATIC
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DABOSSS
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I have a 04 Deville. Yesterday as I was about to leave for the morning, I had placed my
car into reverse without thinking, and backed into a plywood wall separating my garage
from the other one.. No damage to the car, no damage to the separating wall.. I noticed
as I returned home yesterday evening that my reverse lights were not working,upon
inspection I found out my license plate lights were not working but coming on instead
when the car was in reverse and the trunk was open.. Today as I headed out to go to
work I went to pop the trunk to place some things in there, and you could hear the
solenoid clicking but it wouldn't release, after several attempts it finally popped the
trunk.. ( Keep in mind that the trunk of the car never hit the plywood separating wall
and it was merely a small bump.. ) and now the inner bottoms of the tail lights have a
section that will not light up ( sort of like a 1x1 square cut out ) yet the rest of the tail
lamp will remain on as if I am depressing the brake pedal... The tail lights operate as
normal when I have no lights on, the reverse lamps as well as the license plate lamps
are completely screwed up no matter what I do, and the third brake light, well lets just
say, I have seen brighter colors out of a box of crayolas ( i.e Its not working either )..
Am I suffering from a wiring issue, i.e Broken Ground Connection? Could it be a
solenoid on the transmission that has gone bad? Maybe the trunk solenoid is going
bad? It wasn't a hard enough bump to hurt or even leave a mark on the car or the brace
on the wall I bumped, and it still does not explain why the license plate lights come on
in reverse and when I pop the trunk rather than my back up lamps and trunk lamp, and
why the brake lights are not working properly... If anyone has any Ideas, I would greatly
appreciate it as I am about to drive this thing off a cliff and say good bye to Cadillac for
good!

Could it possibly be the body control module? If so, where is it located in the car?


I have checked all the wiring in the back of the car , no burnt wires or broken trunk release... And this morning I noticed that the heated seats are no longer working as they were the day a this began.. There has never been any lighting issues up until now.. I check all lights daily as it is habit for me to do so... So could it be the BCM, or a serious electrical problem that could potentially cause a fire?
Mar 27, 2014 at 3:55 PM
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HMAC300
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check the grounds that I hav e pointed out they may have become disconnected or broken.
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Mar 28, 2014 at 7:22 AM
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DABOSSS
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Just noticed that now the heated seats are no longer working, the auto dim on the rear view mirror is no longer working, and tonight on my way home from work that a message " service electrical system " popped up.. Voltage is at 15.1 idle, and running it drops to 14.6 when driving... so I do not believe it to be an alternator issue. Could it possibly be the BCM going bad slowly killing one component one at a time?
Mar 29, 2014 at 8:31 PM
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HMAC300
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no the body control module doesn't control that. check battery for condition including load test it may have sulfated. also check fuses for seat heater.
Mar 30, 2014 at 8:19 AM
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DABOSSS
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The codes I have managed to pull are Ipm B1004, Ipm B1327, Pcm 1574, Rcc B1009.. checked all fuses and none are blown.. however, I did notice that the battery is a mere 475 cca.. could be that the battery is on its last leg, ( although it seems to be holding quite the charge ) and not able to run everything? Taking it tomorrow for a load test.. Hope that's all the problem is and not something deeper that's gonna cost an arm and a leg to repair..
Mar 30, 2014 at 7:00 PM
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HMAC300
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the battery doesn't really seem big enough for your car with power options. it shold be 800cca so that may be it as two of the codes deal with low power
Mar 31, 2014 at 6:31 AM
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DABOSSS
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Maybe its finally started to take a crap then.. I mean its been in there every since I bought the car a year ago, and Ive never had any real issues with anything electrical up until just recently.. However, with that said, I do have an aftermarket radio on the car.. A Clarion NX702, has the gps, bluetooth, dvd, telephone etc etc in it... But, if the battery was going bad so to speak, wouldn't it show a drop in voltage in the message center of the car rather than saying at Idle its at 15.1 volts and driving its at 14.6 - 14.8? or is that reading coming from the Alternator and the charge its putting out? I'm tying to get as many Ideas as possible before I go out and purchase another battery or whatever I may need to fix this problem...


Mar 31, 2014 at 6:49 AM
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HMAC300
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no because the battery is charging just to SMALL for your car it can't run everything correctly so it sets codes.
Mar 31, 2014 at 7:10 AM
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DABOSSS
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Looks like I'ill start out with a battery and if the issue still persists, I'ill start chasing wiring down... I hope that's all it is is just the battery..
Mar 31, 2014 at 7:13 AM
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HMAC300
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don't start doing wiring issues, rescan it and clear first. remember to reset your anti theft after replacing battery car may not run if not.
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Mar 31, 2014 at 7:19 AM
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DABOSSS
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Thanks Hmac300 You have been most helpful... I'll advise what the outcome is once I get everything taken care of..
Mar 31, 2014 at 7:22 AM
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DABOSSS
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Replaced the battery with one that's 840cca 1000ca and the issue still persists.. I'm at a complete loss for what to do next other than pray someone hits me and totals the car out...
Mar 31, 2014 at 1:35 PM
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HMAC300
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you wil have to erase the codes first then see if they come back on. then if they do we can go from there. even if you replace the battery the codes will remain until they are erased.
Mar 31, 2014 at 1:38 PM
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DABOSSS
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The codes came back up after clearing them.. After searching the internet I ran across someone who was experiencing the same issue, however his was with only one tail light.. Mine are with both yet all the other symptoms are the exact same, ( with the exception of the heated seat no longer working and the auto dim on the rear view mirror.. )
Mar 31, 2014 at 2:04 PM
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DABOSSS
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I don't think I went the cheap route on the battery.. I bought a Optima RedTop instead of your typical battery, which was 4$ less than the Optima!
Mar 31, 2014 at 2:26 PM
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HMAC300
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the body control module has nothing to do with the lights, there is a a rim module in back of seat and the turn sig/hazard switch is wher ethe lights connect . that is why I said check ground because it sounds to much like aground not working when other lights are lit up that aren't supposed to be. the rim also controls the interior lights. here is something I found on the tips page and this may be most of your problem.
If you come across a Deville with inoperative deck lid release, no reverse lights and no license plate lights. This is where to look, left side of trunk by the left deck lid hinge, the wires break from being bent from openning and closing. I soldered in 6 inch extensions on all the wires and taped it up so it would have a recoil effect from now on instead of a sharp bend.
this may be the same problem just happened to be a coincidence.....see pic and do the same thing as it's probably to short on wires.
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Mar 31, 2014 at 3:18 PM
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DABOSSS
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I'm going to tackle that Wednesday or Thursday on my days of before I start my new work schedule.. I'll tell you ( not that I have to ) but you know wiring issues can cause a lot of headache and when something like this is not working properly, It can leave someone frazzled.. Again, you have been most helpful in troubleshooting this issue.. Thank you good sir, and I will advise as soon as I have tackled the issue and post the outcome of it..
Mar 31, 2014 at 3:33 PM
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HMAC300
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wiring is the easy part it's the module sthat screw up or a wire gets grounded an dscrews everything up.
Mar 31, 2014 at 3:37 PM
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DABOSSS
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I know its been on e heck of headache for me, and having to worry about the local law enforcement pulling me over at 4am on my way to work.. Again, you sir are a a scholar and a gentleman.. Will post as soon as I can tackle t Wednesday!
Mar 31, 2014 at 3:43 PM
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DABOSSS
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Hmac300, You sir are a gentleman and a scholar.. After ripping the trunk apart this morning, I discovered 1 wire that had been severed, once I discovered this wire, I grounded it out to the body to make sure this was indeed the exact wire I was looking for.. After grounding it out to the body ( as a temporary ground ) I turned on all my lights, placed the car in reverse, and popped the trunk. ( of course the car was not running ) after walking to the rear of the vehicle, I noticed that all lights were working as they should.. I then began to chase down the other wire and do the work needed to get everything back to its normal state.. I added about 2 inches of additional wire using some heat shrink and a quick connect then applied electrical tape to it... Closed everything up, and all is good... Thank you sir for the information you have provided, It is truly appreciated!
Apr 2, 2014 at 11:43 AM
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HMAC300
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thanks for using 2car pros sometimes it takes a little bit longer than expected.
Apr 2, 2014 at 11:58 AM
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DABOSSS
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If I am ever asked for a site to use to diagnose a problem with a gm car or truck, this site will come highly recommended!
Apr 2, 2014 at 12:00 PM
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DODGET
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How can I be sure the BCM is Bad? I don't have Fuel cluster working and the Climate control doesn't work, all fuses are good, there is no lights on the gauges at all, so the codes dont show up... Thanks Dodge
Aug 17, 2019 at 5:48 PM (Merged)
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JACOBANDNICKOLAS
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Here is the location of the BCM and instructions on how to change it in the diagrams below. Check out the diagrams (Below). Please let us know if you need anything else to get the problem fixed.

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Aug 17, 2019 at 5:48 PM (Merged)
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GENORB
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The passenger side door will lose power sometimes, meaning none of the power windows, power locks or heat seat buttons work. None of them illuminate either if headlights are on. You also can not power down the window by using the driver's side buttons, nor the power locks. This seems to last for a little while, then they magically start working again as if nothing is wrong. I am told it might be the BCM, Where is that located on the car?
Aug 17, 2019 at 5:49 PM (Merged)
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HMAC300
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There are two BCM's in this car one is called the instrument controller and the other is a rear interrogation module. Here are the locations. Check out the diagrams (Below). Please let us know if you need anything else to get the problem fixed.

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Aug 17, 2019 at 5:49 PM (Merged)
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GIGGLERGAL
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Where is the body control module located at on this car?

I have had to replace the head gasket on this car and several things were replaced while it was apart. Now something is keeping the accessories running and it the battery is dead when we go to start it. Any ideas short of getting rid of the car? We put on new battery in it in November and it is a Delco. Since then, on occasion the security alarm will go off on this car also.
Aug 17, 2019 at 5:49 PM (Merged)
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FACTORYJACK
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The body control module, also known as the platform zone module(PZM) on this vehicle, is behind the rear seat back. By keeping the accessories running, is this a visual thing that you know is happening? The random alarm going off could be a door switch, or trunk tamper switch that is intermittently faulty.
Aug 17, 2019 at 5:49 PM (Merged)
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GIGGLERGAL
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[quote:8fc67071a9="gstacey"]The body control module, also known as the platform zone module(PZM) on this vehicle, is behind the rear seat back. By keeping the accessories running, is this a visual thing that you know is happening? The random alarm going off could be a door switch, or trunk tamper switch that is intermittently faulty.[/quote:8fc67071a9]
Aug 17, 2019 at 5:49 PM (Merged)
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FACTORYJACK
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I am not sure if you meant to send a reply. All I got was what I had wrote to you previously.
Aug 17, 2019 at 5:49 PM (Merged)