fuse, bulbs
brake light switch would be most common cause
BAD BRAKE LIGHT SWITCH AT TOP OF BRAKE PEDAL
Are you sure it is your running lights & not just the brake lights? A bad brake light switch (common problem) will cause your brake lights to stay on all the time because they are not wired to the accessory switch, meaning they will work whether the truck is on or off. Hope this helps!
The most likely cause is a bad brake light switch (if none of the brake lights illuminate) but if its only one of the brake lights, try changing the bulb. Even if they still work as running or turn lights because they have a double filament and may still work partially, but not as brake lights.
The most probable cause is that the brake light switch is out of adjustment.
the brake light switch is out of adjustment. Readjust the switch.
More than likely it is the brake light switch that is attached to the brake pedal.
Blown fuse or defective brake light switch.
Nonfunctional Brake LightsOne possible cause of this issue is that the brake light switch is not adjusted properly, or the switch could be defective.
I found this on my 1997 Silverado and found the connection from the wiring harness to the back OS the switch itself was loose, I could wigle it arouns and make the lights come back on.
bad switch on brake pedal? do you have brake lights?
This is usually cause by a stuck brake light switch on the brake pedal. Replace it.