Strange lighting problem with 2004

Critical Mass · February 27, 2014

This is a repost of my introductory post which I may have posted in the wrong place.....

Hello there and thanks for having me aboard. If I may ask a question right away I have a problem with a 2004 2WD Buick Rainier CXL with the auto headlight system. The DRL's randomly come on at any hour of the day or night, ignition power off. They work as they should when the ignition is on. It seems to "take spells". There are times when the DRL's won't turn off after driving, placing it in Park and removing the key. Other times, after initially shutting down as they should, they will come back on a few seconds or minutes after I have turned off, locked the vehicle and walked away. I notice also that there are times when the DRL's stay on during the day when the trans is placed in "Park" when they should go off. There's no forecasting it, it seems absolutely random.

I have been told there is no "DRL module" on this car and the DRL's logic resides in the Body Control Computer. I have replaced the ignition switch and the headlight relay (underhood fuse box) and have the daylight sensor on-hand to try next. But I'm wondering if it might be something simple before I chase every single possible part replacement (next up - the headlight switch itself and then the BCC). Has anyone seen this sort of thing in the past? Thanks, I sure would appreciate the help.

txab · February 27, 2014

Sounds like a BCM issue. Best to have it scanned with a Tech II or equivalent to see what may be found out. I haven't run across this issue before. Odds of my next suggestion being the problem are slim.... but these vehicles are particular when it comes to electrical issues and power supply. Might check battery condition. Battery cables connections and wires. Also check body grounds for poor contact or looseness.

Critical Mass · February 27, 2014

Will do and thank you for your help. I was starting to feel like one of those shows where the idiots run around with night vision goggles and try to scare their viewers with finding "spirits" and such!

Critical Mass · March 13, 2014

Just wanted to report back that the problem seems to be solved. There were no codes and no shorts I could find so I went after the less expensive things first. I had changed, among other things, the ignition switch, light sensor and headlight relay (all in an effort to avoid having to buy a body control module). At long last I got the BCM as well and, after a lot of reprogramming hassle I won't go into, it seems to have solved the problem. For whatever odd reason it did not work until another new headlight relay was installed (first item replaced about three weeks ago) after the BCM was installed/programmed. I would still recommed that anyone seeing this oddball problem change out the relay first as I have found one other person who has seen this problem and says that he "tempoarily" solved it by changing it. For him the problem recurs from time to time but a periodic $40 relay may be better short-term than the expense I just went through. YMMV. Thanks to everyone who tried to help. This is one of the most irritating problems I have ever had. I can now retire the wrench and socket I used to unhook/rehook the battery a couple of times a day.