No brake lights and the fuse is good - 2004 Hyundai Elantra

good set of facts,
all else works car drives day and night, head lamps work.

im reading the cars SM schematic now.
there are other fuses marked brake for brake failures not rear 3 lamps, so I call wrong fuse.
the path is.
under hood fuse box STOP LP fuse good
stops switch at pedal 12vdc one side then 12vdc both sides
pedal down.
the fuse VEH-STOP in IP fusebox.
then wires to lamps 3.and G401

one more, fuse
for tailer and center lamp CHMSL truck
IP box. VEH CHMSL fuse.
but under hood fuse must be good.

Change the bulbs.

Ok, trailer lights are basically separate circuits from the regular stop lights and same with the center brake light.

There is a brake light fuse located in the fusebox next to the battery in the engine compartment. Use a 12v test light to see if it becomes hot both sides of the fuse, when the brake is depressed.

12v Test lights can be bought at a auto parts store for less than $15. Do not get a "continuity light" as these are different. A test light, lights when you touch a terminal and voltage is present using the alligator clip attached to a good ground

Notice that the center stop light does not go through this fuse in the diagram.

I have included a wiring diagram for your vehicle.







If you find the brake light fuse blown, and it repeatedly blows, you have a short to ground from the fuse to the brake lights somewhere. First step is to check the brake lights for a short. and work your way back to the fuse.

Since the turns work in the back, that means the brake bulbs are good. Brake lights and turn signal lights share the same filament in the bulb.
There is a fuse for the brake lights. Then, there is a brake light switch on the brake pedal. You need a voltmeter or test light, after checking that fuse is good. Need to check if fuse has power on it. This is one of those fuses that are hot at all times-as long as battery is connected, voltage should be going through the fuse and up to the brake light switch. Check for power both places. The switch on the pedal is a simple on-off switch. When brake is depressed, the spring loaded switch is turned on-passing power on towards the brake lights.
But then the brake wire goes into the turn signal switch before going on to the brake bulbs...however, since your turns work good, I doubt if there is a problem in the turn switch. First check if the brake light switch is sending power on when switch is on.
Let me know what you find. Good luck.

brake light dont have relay only fuse brakes are hot at all times on gms. in goes from fuse to brake pedal switch to hazard turn signal switch then to brake lights. ck fuse if good go to pedal switch if good go to turn /hazard switch the turn signal hazard brake all use same wire to lamps.

The third or High Mounted Brake Light runs straight off the brake light switch on the brake pedal arm. You say you tested the "brake unit"? I assume you mean the third brake light assembly, and if you get power there when someone steps on the brake pedal, then the bulbs are bad.

The power flow for the brake lights goes like this: Fuse ->Brake switch -> Turn signal switch -> Rear lights. The only difference is, if you have a 3rd brake light in your rear window, that gets its power directly from the brake switch. It does not go thru the signal switch first. So, if you are having a brake light problem, and your fuses are good, check the 3rd light in the rear window, if it lights up (assuming the bulbs are good, no one ever changes them), then the problem is most likely in the turn signal switch, hope this helps!

The power flow for the brake lights goes like this: Fuse ->Brake switch -> Turn signal switch -> Rear lights. The only difference is, if you have a 3rd brake light in your rear window, that gets its power directly from the brake switch. It does not go thru the signal switch first. So, if you are having a brake light problem, and your fuses are good, check the 3rd light in the rear window, if it lights up (assuming the bulbs are good, no one ever changes them), then the problem is most likely in the turn signal switch, hope this helps!

to clear the code disconnect the battery, you could have a bad brake lite swich, its under the dash by the brake pedal

WITH A GOOD FUSE TESTER, TEST ALL THE FUSES FUSEBOX UNDER THE HOOD & INSIDE THE VEHICLE. IF THE FUSES ARE ALL GOOD WITH THE TESTER YOU MUST HAVE A BAD BRAKE LIGHT SWITCH OR A BAD TURN SIGNAL SWITCH. THE BRAKE LIGHT CIRCUIT GOES UP THROUGH THE TURN SIGNAL SWITCH & THEN TO THE BRAKE LIGHTS. FIRST OF ALL IS THE BRAKE LIGHT SWITCH GOOD ? THE ORANGE WIRE FEEDS THE BRAKE LIGHT SWITCH, THE WHITE WIRE PUTS POWER TO THE TURN SIGNAL SWITCH, SO THE LIGHTS CAN BE USED AS TURN LIGHTS OR BRAKE LIGHTS. , PUT A TESTER IN THE WHITE WIRE & PRESS ON THE BRAKE PEDAL. IF THE TEST LIGHT LIGHTS UP, BRAKE LIGHT SWITCH IS GOOD, BY THE WAY THE BRAKE LIGHT FUSE MAY BE LABELED" STOP", THE FUSE LABELED" BRAKE" IS FOR THE ABS SYSTEM. TO CHECK THE TURN SIGNAL SWITCH FOR BRAKE LIGHTS, REMOVE THE PLASTIC COVER FROM UNDER THE STEERING WHEEL, PRESS ON THE BRAKE PEDAL, PUT THE TESTER IN THE SMALL YELLOW WIRE, THEN THE SMALL GREEN WIRE. IF THERE IS NO POWER IN EITHER WIRE, THE TURN SIGNAL SWITCH IS BAD.

If the two rear brake light are working on each side, then fuse and relay are good, check the bulb.