2006 Hyundai Sonota parking lights come on when braking

I had a similar issue on my 2006 sonata and found it caused by the anti theft sensor malfunction. Replaced and solved issue.

that is just a basic 10,000 km service
check engine light on
undo battery terminals count ten reconnect
clears the codes
if check engine light returns
the code will be stored in the ecu

description sounds like an 02 sensor

It can be loose wiring or issue with bulb or the battery is weak or brake light socket getting short somewhere.Car lights getting dim,there are many such common issues noticed.I will share some familiar help links,related to your problem.
Click the link below:---2004 Dodge Ram: High Beam Light is DIM? http://technoanswers.blogspot.in/2012/04/2004-dodge-ram-high-beam-light-is-dim.html
----------Ford Odometer Dims intermittently http://schematicsdiagram.blogspot.in/2012/07/ford-odometer-dims-intermittently.html
---------Turn Signals Don't Work When Brakes Are Applied? http://schematicsdiagram.blogspot.in/2012/04/2005-gmc-envoy-turn-signals-dont-work.html
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Brake light Switch Location? http://schematicsdiagram.blogspot.in/2012/04/1996-buick-regal-gran-sport-brake-light.html
----------- No brake lights on Buick? http://schematicsdiagram.blogspot.in/2012/04/no-brake-lights-on-buick.html
----------- Brake lights not working on 1989 BUICK REGAL? http://schematicsdiagram.blogspot.in/2012/04/brake-lights-not-working-on-1989-buick.html

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These will help.
Thanks.

may want to check the brake pedal switch located on top of the brake pedal arm. If all fuses looks good, replace the brake pedal switch, which can also cause to not shift out of park.

head light control module under dash driver side

your owners manual shows how to replace all bulbs

Could be what is called a body module. Take it to the dealer.

Either all the brake lamp bulbs are burned out... OR, it's the brake switch.. OR, a fuse.

There's a small rubber pad which sits on the brake pedal arm, and holds the brake light switch OFF when the pedal is released. When this rubber pad falls off, the brake light switch is on all the time, not just when the pedal is pressed down. Find the rubber pad, and glue it back on, or make a replacement from cardboard, duct tape, whatever.

Take a look at this PDF, it covers the details of the problem!

http://www.hmaservice.com/files/331/5002040/08-BE-004PDF.pdf

Here is a discussion of the same issue with some further details...

http://www.hyundai-forums.com/t19598-headlights-dim-when-braking-or-taking-foot-off-gas.htm