2009 Ford Focus side lights only work when main beam is on,, any ideas?

owners manual fuses start page 221
https://cdn.dealereprocess.net/cdn/servicemanuals/ford/2014-focus.pdf
lights starts page 90
change light bulbs starts page 246

if just one bulb quit working might be the bulb, connection, wiring or ground wire.
Some cars may have a fuse for different light, or multiple lights. From what I see you do not have a fuse for one low beam light.
Some cars have relays for example high beam lights I don't see a relay for one low beam light.
I think you have a bad bulb or light socket or wiring.
You can try putting the drivers side bulb in the passenger side see if it works that should tell you if it is the bulb.

It's possible the "main" lights elements have burnt out.
I believe it's a single bulb per side with both high and low beam elements inside.
Try replacing a bulb and see what that does.

if you have power to both wires for the bulb then the problem is that the ground wire is connected properly

Did you change the turn signal switch?

the high beams work from a relay in the engine compartment,just replace it,if that dont work then its the switch.

hi kate it realy sounds like a blown fuse far more likely to be that than anything else --- hi beam has its own fuse as do the side lights and also low beam try that if you dont do any good come back to me but i think you will be right .

Push the lever forward to turn on high beams, if they do not work when you do this. You need a new high/low beam switch.

needs a recalibration at ford that should cure it

You need to replace the high/low beam switch

The main/high beam relay/switch must be stuck on high presuming the high beam stalk selector does not operate. Probably needs replacement.