Ground issue, or something else?


Asked by Mar 25, 2014 at 08:28 PM about the 2004 Cadillac DeVille Base

Question type: Maintenance & Repair

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

11 Answers


Pressing on the brake pedal* not depressing it..

2 out of 2 people think this is helpful.

chech you connections and the ground in and under the trunk sounds like the bumper moved enough to disturb somthing


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

2 out of 2 people think this is helpful.

when you open your trunk, there should be a wiring loom that runs along the hinges. try the wiggle test on it with lights on. trunk release, lic plate lights and running lights, all rear trunk area related, prolly bad wire, ( stretched and broken insulation ) in that loom that runs along the hinges into trunk lid. keep in mind that is a general diag, im a euro tech and not familiar with GM products. definatly do not go replacing a BCM yet, i highly doubt that, that is the problem.

1 out of 1 people think this is helpful.

I've had a similar problem, for you maybe a coincidence this may have been a problem b4 you bumped your wall, check the wire harness for any burnt up wires, as far as the trunk is the trunk release intact? its located just above the latch maybe 8 inches from, if its broken that's your problem there as far as the trunk, as for the rest something electrical. The body control is under the back seat or to the left under the hood look in your manual. If you don't have a manual you can get a .pdf online just type year ,make, model owners manual one should come up, good luck.

2 out of 2 people think this is helpful.

also it's unusual that both reverse lights go out at the same time, know that.

1 out of 1 people think this is helpful.

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?


Just noticed that now the heated seats are no longer working, the auto dim 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... 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?


I have the same problem! With the car in reverse and the engine off, I open the trunk and slowly close and open it and the reverse lights come on and off, if i hold it at the position when it comes on the reverse lights will stay on until i move it from its position. The licence plate light will do the same! I still dont know what the problem is! Can anyone help me?

2 out of 2 people think this is helpful.

I have an 04 DeVille with similar weird electrical issues. Like the trunk intermittently not opening with the remote or the interior trunk release. Also cruise control cutting out when I turn on the wipers. Also the traction control not working intermittently Also drivers side electric seat not working intermittently I suspect a ground fault but am unsure as to how to fix it


For those of you who have experienced the same or similar issues, check along the left trunk rail on the lid. thats where I found two severed wires that i was able to correct my situation

1 out of 1 people think this is helpful.

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