Check the turn signal flasher located in the fuse box under the dash.
The turn sugnal and the door switch share the directional switch (turn signal switch on the steering column). Check your tunr signal fuse and your stop light fuse. If all of these are good, chech the wiring connector where the multi-function switch (turn signal switch) connects to the vehicle wiring harness under the dash. If all of those are ok, suspect the turn signal switch as being faulty.