no
no
Yes.
The Switch may be bad. Check the bulbs for the parking lights. Check the fuses / relays for the parking lights.
The GMC dash tail and parking lights are on a different fuse from the brake lights. Check the fuses for a possible blown fuse.
Turn your head lights off before you shut the car off
It places the drive head in a position that is least likely to cause damage to the drive if it is removed or moved physically.
head lights
depends on which lights? inside over head? /Dash board?/Doors? /front headlights?/Flashers?/ turn signals?/ Backing lights?/ Parking lights?/ So which ones ? what Year??
I would start with replacing the head light switch
The ill wire is supposed to be connected with the parking lights of the car. it actually reduces the brightness of your head unit, it is needed because in the night the head unit looks very flashy and the ill wire brings it to a normal level as you turn on your cars parking lights.
Check the relays under the hood. Maybe one is no good.
Check bulbs Check fuse for parking/tailights Check brake light fuse