Could be the flasher unit.
Check the fuses first of all. I think the Durango has two flashers as well, one for the hazards and one for the signals so it could be a bad flasher.
pull one out and put the new one in
The fuses on the 2000 Dodge Durango should be labeled for each part such as the tail lights. The tail light fuse is a 30 A.
The fuse box in a Dodge Durango is under the dash on the drivers side of the vehicle. It is located to the left of the park brake pedal. To get to the fuses to replace them, you need to open the cover.
have you checked your fuses?
Check ground circuit
Defective flasher relay.
open the driver door and then there is a little panal on the side of the dashboard. take it off and inside are all the fuses. then look on the otherside of the panal and it has a list of what fuses do what
Check the fuses and if they are good then check the brake light switch.
Check fuses and bulbs first.
check your fuse box for blown fuses
Could be the switch on the steering column...take it to a mechanic