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Courtesy Lights Stay ON & Run Battery Dead

08-07-2014, 06:29 PM
Several times now I have found that the courtesy lights stay ON after all the doors are closed, and the dash switch is indeed off. This has caused the battery to drain.

I have opened and closed all doors numerous times and the light won't go off. I can't seem to find where the door switches are so that I can inspect them.

The last time this happened I was forced to remove the fuse, then the next day I put the fuse back in and the lights operated correctly.

What could be going on here & how to fix? THANKS

Tech II
08-07-2014, 09:24 PM
You don't say what year.....

But I believe the door switches are part of the latch assembly....a GM scan tool might show(depending on year) which is staying closed...

08-08-2014, 12:41 PM
It is a 95 LeSabre custom.

Do these cars have a courtesy lighting control module? Or are the courtesy lights strickly driven by door switches and the one dash switch?

Tech II
08-08-2014, 03:36 PM
Looking at a '96 manual, I see a MALL module...multifunction alarm, lock, and lighting module.....each door actually has two switches....one is in the latch assembly, which is activated when the door opens...the other is a handle switch, which will activate the interior lights, if the doors are locked, but the handle is lifted.....the other switch inputs are from the headlight switch, and from the RFA module....

08-11-2014, 09:14 AM
Thank you.

Well it is all a bit confusing. I cannot make heads or tails of what the module is called for my 95 LeSabre, or where it is located. I've seen MALL for 97, RAC for 92, and BCM for 96 (I think). They seem to be in different places.

Tech II
08-11-2014, 06:32 PM
Sorry, only have schematic for '96.....I think you mean RAP(retained accessory power) rather than RAC module?

Blue Bowtie
08-11-2014, 09:11 PM
Dumb question, but is the panel interior lamp dimmer slid all the way to the left? That will keep the interior lights on.

1995 uses an interior lamp relay (Relay F) in the relay center just to the right of the glove compartment. It is controlled by the RAC, mounted just below that relay center. The chime module is also located there, so try to identify the module by the connector with ten wires (2 X 5). If you disconnect that module and the lamps remain on, it is likely that one of the door handle switches is stuck closed or its wire is grounded somewhere.

08-11-2014, 10:54 PM
Thank you very much for this information. The interior lamp dimmer is slid to the point just before triggering the courtesy lights.

With laptop by my side, I got inside the dash and located the components. I pulled the lighting relay and the lights went out. I located a module with the following descriptions on it:
Model ABO0303R
White connector
blue connector

Google ABO0303R = Keyless Entry Receiver
Google 25615094 = Body Control Module

When I pulled the white connector, the courtesy lights went out. I plugged the white back in. When I pulled the blue connector, nothing seemed to happen with the lights.

I opened the module and inspected both sides of the circuit board, and it looks clean, but I am aware that components can sometimes fail at the microscopic level. I put it all back together and reconnected it. Now it works properly, but this has happened before. It seems to work then not work (lights stay on all the time) intermittently.

During my tests tonight, I now realize that there is a delay such that once all the doors are shut, it is about 30 seconds or so before the courtesy lights go out (it is my wife's car - I never ever drive it). I think I made some false assumptions before when shutting all doors and the light wouldn't immediately go out.

I'm not sure if this exercise proved anything. I am trying to locate a pinout of this module so if I feel it is necessary, I can possibly cut into the door switch wires one at a time at the module, to confirm if I have a short. I can easily solder the wires back together. This (to me) sure beats pulling door panels off. If anyone can help me locate a wiring diagram for a 95 LeSabre RAC/BCM I'd really appreciate it.

08-12-2014, 09:51 AM
I went out to the car this morning, opened a door, closed it, and the light did not go out after a few minutes. I am convinced it is a fault in the BCM so I just ordered a replacement from Ebay.

08-22-2014, 07:11 AM
I finally received a replacement BCM, installed it, and re-associated the keyless remote to it. The same anomaly is still happening.

Even with both connectors of the BCM disconnected, I could turn on the dash courtesy light switch, turn it off, and the lights may or may stay on. So let's say they stay on: When I pulled the courtesy light relay, the lights go off. Then plug it back in, the lights remain off - huh?! I took apart the relay but couldn't detect a fault in it. I swapped relays and the same thing happens sometimes.

This is maddening. I cannot find rhyme or reason what is causing my courtesy lights to stay on. It is not in the BCM and it is not in the relay.

Could I have a "faint" short to ground in one of the door switch or dash switch circuits which is keeping the relay engaged, yet not able to re-engage it once disengaged?

I really need a wiring diagram for this but cannot seem to find it (95 LeSabre). Where do all the door switch wires & dashboard switch wires join at? I'm guessing they do not join inside the BCM. So where do they join? I'd like to separate them (cut them) one at a time and see if I can detect which switch may be shorted to ground.

EDIT: My new theory is this: Since I believe that a ground is what engages the courtesy light relay (unsure), then when the dash switch is closed, I'm guessing it is providing ground, and when the doors are open, I believe the BCM must be outputting a ground to the courtesy light relay. So at some point, the dash wire and the BCM output must join together (right?) before going to the courtesy light relay. Therefore, I believe I have a faulty dash switch, or chaffed/grounded wiring between dash switch and relay, or chaffed/grounded wiring between BCM and relay. If I could find where the dash switch wire and the BCM wire come together, I could separate them and test. I don't think the problem is in my door switches simply because when I disconnect the BCM, and use the dash switch to turn on the lights, when I turn off the dash switch, the lights stay on (sometimes). To me something is chaffed and moderately grounding out.

Where do the dash wire and BCM wire join what colors are they?

Tech II
08-22-2014, 09:17 AM
As I said before, I don't think the BCM has anything to do with this.....it's the MALL module.....go to any Buick dealership......they can copy pages from the manual for you.....may charge you some money for the printing......

Once you have the schematic, and you see the inputs to the MALL, you can disconnect the harness and check for a ground from the door inputs.....unfortunately, the driver's door is a single input, while the other three are in parallel.....hopefully it's the driver circuit.....otherwise, you will have to separate the soldered joint to check which of the the three other doors is the culprit....OR, you will have to remove the three door panels, one at a time, and disconnect each switch, and see if the ground is gone....

08-22-2014, 09:38 AM
From what I can tell, the MALL in newer model cars is essentially the BCM in older model cars. MALL and BCM are essentially the same thing. The problem is not in my BCM/MALL. And I don't believe the problem is with my door switches.

I need to find where the dash switch wire and the BCM output are joined (which powers the courtesy light relay), and what colors the wires are.

08-25-2014, 06:51 PM
I may be ghost-talking here but if only it helps someone in the future who has a similar problem in this ever-thinning fleet of 95 LeSabres, then it was well worth it.

I have found that one sure way to keep the courtesy lights from staying on is to pull the courtesy light relay (relay F) (obvious).

I also took note of the wires going into the BCM. There are 2 plugs, a blue plug and a white plug. The blue plug has 8 wires and seems to affect keyless remote & of course the locks. The white plug, however, directly affects the courtesy lights.

The white plug has 5 wires:

It is my belief that the BCM delivers ground to the courtesy light relay through one of these wires. And, at some point this wire couples with a wire coming from the dash courtesy light switch at which point it connects to the relay.

One day I'll get to the bottom of this mystery. For now, no courtesy lights.

And for a little comic relief: My wife and daughter have been having the habit of popping the trunk, unaware to them, and leaving it unlatched for hours on end until one of us discovers it. Perhaps the aftermarket keyless remote is partially to blame. Nonetheless, this too has been causing the battery to run down. I have finally disconnected the trunk light due to this ongoing risk of them getting stranded.

Blue Bowtie
08-26-2014, 04:50 AM
As stated previously, the vehicle uses an RAC module, not a MALL. In addition to door jamb switch inputs on Pin C, there are door HANDLE switch inputs on Pin K. This might help:


08-26-2014, 11:13 PM
I went through the same thing as you did. It is easy to find the problem.
Mine ended up being the switch (the one you push to make the lights go on and off.

I'ts easy, because there is a procedure you can do. It puts it into diagnostics mode for that problem. I will look and see what you do. It's like you turn a switch on and off 6 times, push this and then push that twice.
When in diagnostics mode, you hear the ding, ding, and as you open up each door, if it keep dinging, it's not it. I went through all the doors, nothing. I went to the light switch, it showed it was the problem. I changed it, and it fixed it.

One thing that made me mad was, I went to the dealer and they said it could cost thousands to "go through the wiring."

I put it in diagnostic mode and had the problem figured out in a few minutes.

I will post back when I can find it in the manual. Funny thing, I bought a new BCM and it wasn't it. I still have it, brand new. Wish I could of sold it to you.


08-26-2014, 11:35 PM
I see mine is a 97, not sure it will be the same as 95, but could be. It may have another "Diagnostic Mode Procedure or not at all.

Here is my post I did about it.

WOW!! GM Diagnosis is GREAT!!

.....So many things it could be, each door has a door handle switch, could be the BCM, dimmer swich, short in a wire.

I got my good old GM Service Manual and did the Interior Lamps Diagnosis.

Ignition Switch to RUN,
Press and hold the power unlock switch,
Cycle the Headlamps 6 times,
Release the Power Unlock Switch.

I pulled the front LH door open. Heard one Bong. Did each door, with a bong each time. I turned the headlights on, Bong.
I then turned the Interior Lamp on, no bong.

This took a total of about a minute. It was soooo cool, I did it again, with the same results.

A couple years a go, the Dealer told me it would be a lot of money to do an electrical diagnostics. "They would have to get in and check a bunch of wires. Electrical stuff gets real expensive, quick." Took me about a minute.

This GM Diagnosis is GREAT!!!


08-27-2014, 10:35 AM
Thank you for the wiring diagram BlueBowtie; it may prove to be useful at some point. However, I suspect your diagram to be from a year newer than a 95 LeSabre.

1995 uses an interior lamp relay (Relay F) in the relay center just to the right of the glove compartment. It is controlled by the RAC, mounted just below that relay center. The chime module is also located there, so try to identify the module by the connector with ten wires (2 X 5)....

There is no RAC module, or chime module that I can see, below the relay center. There is a BCM next to the relay center behind and to the right of the glove box. Your diagram shows approx. 24 wires coming from the RAC module. My BCM has 8+5=13 wires coming from it. My BCM looks nearly identical to this with the exception of the the handwriting (and has this number stamped on it: 25615094):

Thank you for the diagnostic info. I don't think my 95LeSabre has this feature but I will try it.

Blue Bowtie
08-27-2014, 05:00 PM
Sorry, let's try again. I updated the drawing. That one IS for a 1995 Le Sabre.

09-16-2014, 01:43 PM
@Blue Bowtie
That diagram is EXACTLY what I am looking for. Thank you. Now I know I need to trace down & temporarily cut the dark blue wire coming from the PANEL INTEROR LAMP CONTROL.

09-30-2014, 08:23 PM
OK...I finally got into the wiring again. I removed the relay/fuse center and took the back cover off and identified 2 dark blue wires going to the courtesy light relay. I took a gamble and cut one of the wires and viola it was the right one. Now the dash courtesy light switch no longer works which is exactly what I wanted to do.

For anyone interested, the wire I cut is the wire that is closest to the perimeter of the relay center.

Now only time will tell if the short was in the dash courtesy light switch circuit which has now been removed from the equation.

Connected the relay again and confirmed repeated correct operation. Now to observe carefully day after day to make sure the courtesy lights go off automatically every time.

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