How do you change a headlight in a 2006 buick lacrosse cxs?

Sampson, sounds like a bunt out bulb, which will need changed.
If you feel comfortable doing it yourself. Basically three screws, and you have to pull one plastic fastener from the fascia (bumper) and pull the bumper back a bit, and pull the assembly out. I believe it is in the manual, not bad to do. I will post a link to tell or show you how to do it. Press the helpful button

Headlight Change 2005 2009 Buick LaCrosse 2006 Buick LaCrosse CX 3 8L V6

2008 Buick LaCrosse Headlight Replacement

Thread how do replace the headlight bulb in 2005 buick lacrosse

Headlight Bulbs

Here's a link on replacing your head light. Headlight Change 2006 2011 Buick Lucerne 2006 Buick Lucerne CXS 4 6L V8

Hi David,here's a video showing how to replace your head light. Headlight Change 2006 2011 Buick Lucerne 2008 Buick Lucerne CXS 4 6L V8

Headlight Change 2006 2011 Buick Lucerne 2008 Buick Lucerne CXS 4 6L V8

chances are the wire connection from the unit to the car has broken.

Horns on most late model GM cars are behind or below the headlight. Many of these cars have headlight that are very easy to remove. The are held in place with plastic slides.... you pull the slide or release (there are usually 2) and the headlight assembly will come out of the body. Then you can look for the horn.

firing order written on intake manifold

The P0496 DTC code is a generic code which applies to all vehicle makes. A quick search on the 'net shows that this code seems to be more common with GM (Chevy, Pontiac, etc.) vehicles. In Acura, Honda, Hyundai, Kia, and Mazda vehicles, this code is described "EVAP system high purge flow" which is the same thing.
try use maxiscan us703 to clear the fault code.