See also:

Replacing exterior bulbs
Check the operation of all the bulbs frequently. ...

Trailer lamps
Trailer lamps are required on most towed vehicles. Make sure all running lights, brake lights, turn signals and hazard lights are working. Do not splice into the vehicle lamp wiring for trailer lam ...

Signal indicator mirrors (if equipped)
When the turn signal is activated, the outer portion of the appropriate mirror housing will blink. This provides an additional warning to other drivers that your vehicle is about to turn. ...