Either the brake light switch or on brake pedal there is a button that pushes the switch and it fell out.
Do you mean What does it mean when the brake and battery lights come on in when it is already started? Check your alternator may be its not working well it cause the battery sign comes out.
It could, if the lights are on all the time.
bulb gone? fuse burned? battery dead?
It's probably your Alternator that is going bad. That is if the battery and brake lights came on at the same time.
Alternator has/is going bad.
fuse, bulbs
A dead cell in the battery will cause it to loose it's charge overnight. The only fix is to replace the battery. Also if something is on drawing power from the battery it will run it down overnight. Look at all lights. Interior, under hood, trunk, give box, brake lights, etc. It can also be a stuck relay.
brake light switch would be most common cause
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!
BAD BRAKE LIGHT SWITCH AT TOP OF BRAKE PEDAL
The BOO (Brake On/Off) Switch may need to be replaced. If it is bad, it would cause the brake lights to NOT illuminate when the brake pedal is applied.
Possible ground issue at the taillights.