2003 GMC Drivers side head lamp

2010 Chrysler Sebring one headlight high beam dead?, there are 4 beams , tell them all first.
can be lots of things, besides lamp, wires, and fuse.
did you be sure to check all 6 fuse for HL?
some use breakers. or mix of breakers and fuses.
wow, not told if car drives perfectly in he day
not told country if in canada and those stinky DRL bad
got Daytime-Running- lamp , up in the Klondike. (LOL )
head lamps work key off. or out of car,
they operate that way by law, and must be bright tested that way.
now I will read the shop manual for you now,.
on any car this new it must be scanned firs as this car has lots of computers on board, ever heart of BCM the body brain
will on most cars this run head lamps and well lots of things, even blinker and parking lamps and more.
and not scanning it first is a huge waste of time.
USA answers only by me. (no docs outside for me)
this car has 3 brains for HL.
1 left front, 1 right front called HL drives
and the main one called. MTIP, module total integrated power.
runs all lamps,
case in point 1 DTC error scanned, you see AND LOTS MORE DTC for HL

B1634-Left Hi Beam Control Circuit High
causes

(L33) HIGH BEAM CONTROL CIRCUIT OPEN
(L33) HIGH BEAM CONTROL CIRCUIT SHORTED TO VOLTAGE LEFT HIGH BEAM BULB TOTALLY INTEGRATED POWER MODULE learn to scan all modern cars first
and not go broke guessing wrong./
sorry the car must be scanned for sure 2000 and newer cars

Check the wiring on that light. Also check the bulb with a couple of wires to the battery, or swap the bulb left to right to make sure the new bulb is okay.

id just replace the bulb, socket,and your sure you checked all fuses

seems you have several different problems. High beam working and no low beams=dimmer switch is bad. Reverse lamp not working=bulb socket bad,wiring broke,bad ground at back
Brake light on drivers side stuck on=brake light switch

What year and model is your subaru ?

Is it a singe ground issue? Fuse? ?????????? Without doing some testing we would be just guessing. You need to test the electrical circuit to know for sure . Voltage drop testing !
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You need a wiring diagram so you know what wires to test . Free wiring diagrams here http://www.bbbind.com/free_tsb.html Enter vehicle info. Year , make , model and engine size . Under system click on lighting ,then under subsystem click head lamps . Click the search button then the blue links. Look at the wiring diagram to see what all is involved in making the head lamps work .

On a 2008 Prius, If both High beams work but only one side has working low beams, then it is most likely a fuse. So before breaking your knuckles to change the bulb, check the fuse first. I found out the hard way as my mom distressed to me that her drivers side headlights were out. So without checking to see if low and high were working, I proceeded to remove and replace the bulb - ouch! There are 4 10 amp fuses that protect the circuits for low/high beam function. They are under the hood in the fuse box on the drivers side and they are marked on the box cover. Check them before changing the bulb.

Well, the problem is that I dont know the reason, you should investigate. There could be issues with lamps (must get new) or electricity problems (must head to auto-service)

The problem is a Headlight module. Fuse box under the hood has two black modules side by side, the one on your right is the headlight module the one on the left is the fan module. Try swapping them, if the headlights work replace bad module, don't drive vehicle with the bad module in the fan slot. Mine kept going bad because I had a high intensity bulb on one side.

When you turn on your head lamp do you notice that you also have rear tail lights that are lit up as well? I have noticed on some occasion, both front headlamp assemblies could possibly be blown at the same time. One of the most important tools for checking to see if you have power on the low and high beam circuit will be a automotive test lamp, you can purchase these at most auto parts stores.

Either both bulbs are bad(I've seen it before) or your
dimmer/headlight switch is bad. If you can without pulling the bulb, pull plug from the light. If it's a 4 lamp system pull the low beam. Do this on the left side as the right feeds from the left. With a 12v test light, check for power. (with lo beam on) if you have
power, change the lamp, if you don't it's most likly
the dimmer switch at the steering collum.
Hope this helps Good luck