2004 Century: door ajar light on, dome lights will not turn off

01-16-2016, 09:27 AM
Okay, so the door ajar light came on the other day and the interior lights would not turn off when I turned off the car. This is a 2004 Century. I ended up removing the fuse so that I can be assured that the battery wouldn't drain. The problem is in either the driver or left passenger door. I couldn't see any door switches like I've seen on other vehicles so I'm wondering if this is a latch issue or an electrical issue. Any help would be appreciated.

Blue Bowtie
01-16-2016, 10:14 AM
That's a valid assumption. There is a switch within the latch mechanism which senses the handle position. Given the "wonderful" rain/sleet/freeze/thaw weather spell we've had recently (and are about to have again this weekend) it may be a simple matter of water incursion and freezing. If you can get the vehicle into a heated space it may resolve the issue. This is one of the FEW instances where something meant as a metal preservative and NOT a lubricant, like WD-40, can be use successfully. Its formulation tends to drive away water and leave a thin film of oil (WD= Water Displacement). You may have to remove an interior door panel to access the latch to apply the protectant.


01-16-2016, 11:35 AM
With your weather the earlier suggestion may be the correction - not sure! However I think in this vehicle they have flat metal sensors that detect FULL door closure. Check on the door and the door pillar to see if there are any sensors - If so clean with a WD40 type cleaner. I have an 02 Cougar (Grandson's) that had the same problem and I adjusted the Closure Bar on the Pillar slightly (up, down, in and out) on each door until it sensed the doors were fully CLOSED. I marked/scribed the original location before I began so I was able to secure it back to original position. In this vehicle (Cougar) it was the big Hatchback door that was causing the problem. Made it a slightly tighter close and the Door Ajar lamp extinguished.

01-16-2016, 02:18 PM
I tried the WD-40 trick first without removing anything since it's really cold here right now. It worked. I'll be keeping in an eye on this. Thank you!

01-16-2016, 02:20 PM
I didn't see any such sensors on the vehical... I think the closer is in the latch as blue bowtie suggested. Right now the WD-40 did the trick and I'm very happy about that. Thank you for the speedy reply.

Blue Bowtie
01-16-2016, 06:06 PM
Bob is probably right about Fords, but the Buick certainly uses contacts inside the latch to prove closure and signal the BCM. The other electrical connector is for the power lock actuator.

Another thing you can try is to open the suspect door, use a Phillips screwdriver to simulate the striker, and close the latch plate fully to see if that satisfies the BCM. DO NOT attempt to close the door in this condition - You must first release the latch plate which may also require the screwdriver while operating the door handle.

I know it's getting pretty windy and dark, but it isn't going to get any better for a few days.

You have one hour before the game starts...

01-16-2016, 06:10 PM
The WD-40 worked for now. Thanks for all your help! Have a great night.

Tech II
01-18-2016, 08:31 AM
Have to agree with Blue Bowtie.....it is the door ajar switch inside the latch mechanism, causing the problem....surprised the WD-40 did the trick.......

These damn things can be so intermittent...only way to know for sure, is to hook up a scan tool, and read the info from the door ajar switches, while pulling on each door(without opening it), and looking for a change in info on the scanner....only a high end scanner like a GM Tech II scanner has access to this data...

Blue Bowtie
01-18-2016, 06:38 PM
Tech - I wouldn't normally bet a plugged nickel on WD-40, but the weather around here has been just right for moisture and ice formation. This is the only thing WD-40 is good for. If I hadn't been experiencing the same kind of weather I would have advised he pull the latch and clean the contacts (been there).

Tech II
01-18-2016, 08:37 PM
I have used WD-40 on the inside of distributor caps, with success(temporary)....so what you suggest is a good trick to use......

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