Have you recently added a trailer hitch? Somewhere the wires have become crossed and that is a common place for it to happen. If anything has been done to any of the lights, that is where I would look first.
Turn on that fast blinking signal light and check to see if the front and rear signal lights are both working, chances are you have a burned out bulb. If both front and rear bulbs are flashing fast, replace the flasher relay.
There is essentially no restriction on using brake lights and turn signals at the same time, as they both signal actions/intentions that are often used in conjunction with one another. The brake light signals that you are using your brakes and slowing down, and the turn signal shows your intention to turn. As you will usually slow down as you come up to a turn, there will be many situations where both signals will be on at the same time.
you lost ground to one of the light sockets or hqve a bad socket in one of the lights
Check and make sure you have the correct bulb. The turn signal/brake light is a dual element bulb and if you have a single element it does not work properly.
Stop and look both ways..then proceed,unless a rail is down or red lights are flashing.in that case,wait until the rail recedes,or red lights stop flashing.
It needs checked out but both the hazard and brake lights go through the turn signal switch.
Warning lights are important to pay attention to and know warning lights. If seat belt lights flash, and an air bag light flash, it means there are problems with both parts.
your brake light switch is probably out
no both systems have a separate flasher
Both turn signals work when they want to. The hazzard lights work just fine. All bulbs are great. The turn signal indicator will flash inside the car for a few seconds and then stop. The outisde turn signal lights stop too.
You have an electrical fault
Although both signal lights and stop lights are within the same lens, they operate on different wiring. The bulb will usually have two filaments, one for stop and one for signal. If the brake lights are not working, the problem is probably a blown fuse or a faulty break light switch.