I have a 2002 Toyota Highlander. The rear right turn signal and break light don’t work when I apply the brakes. When I use the turn signal or brakes while driving or parked there is no problem, but once I apply the break the back right side does not work. The light bulbs also burn out faster on that side.
Your post does not make sense as written. So answer these questions.
Does the right taillight work when you turn on the headlights?
Does the turn signal work with the head lights on?
Does the turn signal work with the head lights off?
With the headlights and turn signal off, will the right brake light come on when you apply the brakes?
With the headlights on and the turn signal off, will the right brake light come on when you apply the brakes?
If not, does the tail light go out when you apply the brakes?
With the headlights and turn signal on, will the right brake light come on when you apply the brakes?
If not, do the tail lights go out and the turn signal stop working?
Do you have a trailer hitch and wiring on this vehicle?
If you do, how many pins are on the trailer connector?
If you do, do you have a trailer?
Different bulbs or at least different elements of the same bulb are used for the rear brake lamp vs. the turn lamp I’m guessing. hmmm … and they both work ok and illuminate separately, but when you press on the brake pedal and turn on the turn indicator at the same time, neither lamp lights up?
A loose ground wire could cause this symptom. The ground wire from the bulb socket to the chassis. What happens is there’s more current flowing in that ground when both are turned on, and the voltage drop due to the extra current can cause the voltage to rise enough the lamp won’t light. Check that the ground wire for that lamp cluster is securely connected to the car’s chassis, and make sure the bulb ground or socket ground are not corroded.
To see if there is a faulty ground connection on the right side run a test jumper lead from a known good ground point to the ground for the lights. If they now work try cleaning the connection for the lights or check for a bad connector connection.
It’s most likely the socket, trust me, we’ve replaced a lot of them, not only for our customers, but on my own 2003 Highlander.