Sunroof Leaks Caused Multiple Electrical Problems


Full Member
Wolcott, CT
Buick Ownership
2010 LaCrosse CXL AWD
One morning after a heavy overnight rainfall, it started raining from the overhead control panel inside my high mileage 2010 LaCrosse. I also noticed that the left side roof pillar fabric was soaking wet and there was substantial water on the driver's floor. This resulted in the following symptoms over several weeks:
Engine would not stop when the start/stop button was pressed; parking brake system warning came on and parking brake would not work; while driving, the automatic transmission popped up a warning message and stopped up-shifting; another time the "reduced engine power" message came on and the car wouldn't go over 40 mph; when starting car, the check engine light would come on popping up P0603 among others. I finally took it to my local dealer, Stephen GMC Buick in Bristol, CT (who I highly recommend). They found that the thru-firewall connector for the harness that connects the main computer (under the hood) to the BCM module (under the dash) was wet. They took it apart and cleaned the contacts. Problem fixed! All this because of a clogged sunroof drain. They charged me for two hours labor, no parts. This car has 180,000 miles on it, does not burn oil, the front end and running gear is all tight, the body and interior still look great. Thank you Stephen GMC Buick. I am a happy camper!


Full Member
Buick Ownership
2007 Lucerne CXL. and 1995 Lesabre currently, past 1973 Riviera, 1968 Riviera
Glad you found a dealer that still takes care of the customer and hopefully other sunroof owners will check their drains before they find out too late.



Full Member
Las Vegas, NV
Buick Ownership
2017 LaCrosse 1SL
This is exactly the sort of thing that I'm grateful to not have a sunroof. When I did I liked the extra light, if I remembered to open the shade. But for the most part it was an impending fail point that I paid extra for.

Glad you got it sorted and for relatively cheap. Make sure to thoroughly dry things out, maybe run a power extension and put a space heater in the cabin to speed up that process (otherwise mold/mildew isn't far behind).