The scanning beam is not going to the left, it is always at the right and says nock nock, even if the belt is running slowly but maybe the belt runs wrong way.

no country told this is a world wide forum, and cars are not the same world wide at all, vast differences. (by laws too)
quesiton #2 is this car fitted out with DRL, daylite running lamps>??????????
well fuses are first. check them first we do.
then scan the PCM using scan tool (obd2 ,2008 or newer tools)\
USA answer?
the PCM will tell you why,
the owners guide ,in glove box see chapter fuses/
see head lamps? HL :? fuses,??? OOPS NO FUSES !!!
focus , not focus Electric or Focus RS car,. right.
the BCM runs the lamps and has no fuse for any pair of lamps
it uses electronic regulators to NOT need fuses. 2018 auto lamps.
the left and right bcm lamp drivers are not he same driver.
so only one side fails. see?
F74 fuse blow kills them all up front. 10 lamps dead. so is not this.

here is my guess, manual lamps fail low beams.
both lamps are bad.
or wires cut or shored to them. but no wire can do that,
there are redundant wired sides, so both can;t fail by DESIGN
\even 2 grounds, left and right not the same.

so learn the scan this car every time if fails
fore sure now.
or test the lamps 1 by1 , unplug them and see if low beams read 0 ohms if not the element it burned out. on both.
scan it and see , left right dead lamps low/??????????

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

https://www.fixya.com/cars/t8706315-2003_gmc_yukon_xl_denali_low_beam

Maybe a problem with dimmer switch? You have lo beam fuses and low beam relay in under hood fuse box, use a test light, check for voltage at the lo beam fuses with lo beams turned on. I wouldn't think both right and left lo beam fuses would blow at the same time.
The bcm grounds the lo beam relay. The dimmer switch lets the bcm know what's going on, so the bcm will ground the lo beam relay.
I can only help with testing. I looked at info for Silverado.

Normally there is not way to tell if you belt is going bad, meaning its running good and near breaking point. Usually timing belts should be changed every 100 150k miles. Sometimes even less depending on what kind of belt you get. So if you car/truck is above 150kmiles or even near it id change it.

When change the belt, make sure you have your timing marks lined up before taking the old belt off. If you do this right, nothing will move when you take the old belt off and you wont have to worry about timing the motor. Also it helps to take number one cylinder spark plug out and put a screw driver inside of it when rotating the motor to see where Top Dead Center (TDC) is. If you do that make sure you rotate the motor slowly, you don't want to rush and damage anything. And as always make sure you have a manual!

On these cars the headlights get power from a right and left fuse and the headlight / dimmer switches provide the ground circuit. Both headlights are connected to one ground wire for high and one for low beam. So if one works and the other does not, the problem should be in the wiring before the headlight switch. Red is for high beam and red-white is for low beam. You should be able to jumper the red-white wire on the right headlight and make the low beam circuit for both sides work to test it.

That sounds like a hardware problem. Please contact Lexmark Technical Support Center for assistance on this matter.

go to freewarefile.com and up on the left side you will see advacne system car 3 click on it and run the dig at top and left to help speed up mechine again

Any oil is better than no oil. Put some motor oil in there before you run it any more, even if it isn't exactly right.

left to right...
1. empty
2. e flashers
3.horn, brake lights
4.clock, trunk light, inside light, radio
5. rad. cooling fan relay (AC only)
6. right side running lights
7. left side running lights
8. right high beam and indicator
9. left high beam and indicator
10. right low beam
11. left low beam
12. reverse,turn signal and inst panel
13. main and transfer fuel pumps, auxiliary air reg., ox sensor heater
14. license plate and glove box light
15. wipers
16. rear defogger
17. heater blower (no AC)
18. cig lighter
19. rad cooling fan (no AC)
20. Heater blower (AC)
21. rad cooling fan (AC only)
22. empty
23. Ox sensor, idle stabilizer,seat belt warning relay, (Digifant only, control unit, idle boost control, idle boost valve)
24. inst panel lights, heater control lights
25. reading lamps
26. empty
27. empty
28. empty

Hope this helps...;-)