One of my brake lights wont turn on

Replace that bulb. All those functions are from the same one filament inside those two filament bulbs. One filament is for park lights, and the other is for turns and brake light.

Has the vehicle been in an accident on the left rear side. First check the bulb to be sure it is not defective, trade it out with the side that works properly to test. If the bulb works well then My thought are you may have a shorted wire. The turn signal flasher works by heat build up within the flasher the heat is caused by the load of the bulbs, the load heats the metal spring causing it to open the circuit then as quickly as it cools down the circuit closes again lighting the bulbs.
There is also a possibility of a defect in the turn signal mechanism on the steering column. The turn signal switch on many models does three different things on many models that use the same bulb element / or bulb for brake and turn on rear of vehicle. It controls the circuit for brake light by sending power both left and right side rear when turn signal is in neutral position then when turn signal is in left turn the switch cancels brake light power to left side rear and supplies flasher power to left side while maintaining brake light supply to the right side rear, and so on opposite when the right turn is chosen on turn signal switch. The turn signal indicators on the dash normally run off the same circuit as front turn signal bulb only which is also controlled by turn signal switch. Front has turn signals but no brake light.
I think there is an additional load on the left side rear turn circuit and it could be either a wire that is shorted or the turn signal switch if the same bulb element is used for both functions.
Often times if trailer lighting is connected the flasher will also blink a little faster because of the extra load of additional bulbs.

There are 2 fuses for parking lights left and right side. so it can be 2 relays. located in the box in the front.

The bulb for the turn signal/brake light is a double filament bulb. It will come on with the lights on, but should light the second filament, making it brighter, with the brakes applied or turn signal on. It could just be a bad bulb, but one common problem on these years of truck is the rear light circuit board and requires the whole assembly to be replaced. Start by checking the bulb first though.
Hope this helps. Good luck!

That's a new one. I have a 2005 van and never seen that message. Are all the lights working on the exterior of your vehicle? I assume that it would be an exterior light since you would not need a warning about an interior light. You might want to also have someone start the vehicle and operate all the lights including the brake lights and you walk around and see if anything is not working. The fuse panel is located in the engine compartment if you want to check that also.

Lights to check:

Turn signal front and back
running or "parked lights" when headlights are off. These are the orange ones below the head light and the running bulbs in the rear.
Brake lights to include the strip at the top of the rear hatch.

If you find one burned out, I have a proceedue for replacement if needed pasted below. Hope this helps....

Chevy Uplander (2005) Headlight bulb or turn signal replacement:

It is important to ensure all lights are working for the safety of you and others on the road.

Headlight:

In order to gain access to the head light bulbs, the headlight assembly must be removed. There no easy way to gain access to the lamps with the assembly installed. Open hood. Use 10mm wrench to remove faster on top of the light assembly closest to the rubber hood rest. You then need to remove the silver looking pin near the grill. This pin is snapped in place. Rotate counter clockwise and then pull pin straight out. The light assembly will now have to be pulled past the front header panel near the grill. Use care as the light is pulled past the grill panel. When you have this done there is one more fastener holding the light to the vehicle. On the far out side edge of the light near the fender panel, there is a ball socket fastener holding the light to the vehicle internal frame. Pull straight forward to pull the ball pin out of the socket. It will take a lot of force, but be careful as you apply force and pull light out forward. My light took some wiggling up and down, left and right until the ball released. Once the light is out, the lights are accessible. Both the normal and high beam light sockets rotate counter clockwise to remove from the headlight housing. There is a very tight detent in the counter clock rotation which took a fair amount of force. Once it "clicks" past that point during rotation, the light socket was able to be pulled from the light housing. The light bulb pulls straight out of the socket. Please use a clean towel or gloves to protect your fingers. Bulbs can sometimes crack and cut your fingers. Also, when you install the new lamps, use a towel or cloves as not to get oil on the glass which can cause uneven heating of the glass and crack it under use.

With the light assembly out, it is now easy to reach down into the vehicle to change the turn signal. This lamp is colored since the turn signal lens is clear.

Once bulbs are replaced, please test them before reassembly just in case of any issues. The headlight assembly ball socket will snap back into place easy. Once that is in, press the rest of the light back to its normal place. When the holes are lined up, place the silver colored rod back into its slots all the way down the inside of the light assembly. It then can be rotated and locked back into place. Reinstall the 10mm bolt on top of the light assembly near the rubber hood rest. Again check the lights to insure nothing is out of order.

Rear Lights:

To gain access to the bulbs to the real light assemblies, you must remove the light housings. Open up the rear hatch. Use a T30 Torex screwdriver and remove the two screws on the inside of light. Once those are out, the light assembly can be pulled out slightly from the vehicle. On the side of the van, the light assembly is held in place by two snap fasteners. Pull the light towards the rear of the vehicle to disengage the outside edge fasteners. Once done, the light assembly will be loose and the bulb sockets are accessible. They rotate counter clockwise release from the housing. The bulbs themselves pull straight out of the socket. Please use a towel to protect your hands and to make sure no oil gets on the bulb surface. Once done, reinstall the light assembly by first lining up the two plastic fasteners on the outside edge to the vehicle panel and press the light assembly to the vehicle. Reinstall the two screws and test light. Be sure to have someone press the brake for you to ensure your brake light works.

Bulbs:

Front:

Low beam/ high beam lights: (12362LL) Phillips (H11LL)

Front Turn Signal: 4157NAK amber color

Corner marker lamp: 194FH4 clear

Rear:

Brake/turn light: 4157LL (clear lamp)

Lower back up light and top running light: 3057XX (Wagner) (clear lamp)

www.autobuyguide.com gives a list of factory defects. This is one of them. #04V527000 from NHTSA. Contact Chevrolet at 1-800-630-2438 It says they will replace the whole assembly.

Kinda sorta,you have check for power inside the bulb socket when the brakes are applied.
If you dont have juice there then you will have to find out if the brake light switch is working.
I believe ther is a brake light relay box in the trunk,I dont remember where,but it could be defective.
Listen to this the light assembly on the honda do go bad. the whole light bulb assembly the silver plastic unit,get one from thejunk yard and change the whole thing.Look at it it's easy to do.

1. Pop the trunk
2. Remove the two Phillips-head screws holding the cover on
3. Using a slotted screwdriver, pry the cover away from the side of the vehicle (carefully!)
4. Twist the bulb seat away from the cover, a 1/3 turn counterclockwise.
5. Pull the old bulb out; discard according to any local laws
6. Push new bulb in
7. Test both your turn signal functions and brake light functions!!!!!
8. Return bulb assembly to cover; twist 1/3 turn clockwise to reattach it
9. Push tail light assembly clips into the seats on the side of the vehicle
10. Replace the two Phillips-head screws holding the cover on
11. Close the trunk; clean up

You should probably check the multi-function switch. This is the turn signal switch assembly. The brake lights on most all vehicles, are routed through the turn signal switch, and then go to the rear of the vehicle. This is done because the brake light bulb on many vehicles is used as a turn signal bulb as well, and there has to be a way to break the connection from the brake light circuit to allow the turn signal to operate on the same bulb. Use caution when checking or removing the multi-function switch assembly, as you must remove the protective cover from the steering column, and there is an air bag harness located inside. If in doubt, always refer to the manufacturer's service guidelines for making any repairs in or around the steering column.

This is a classic example of turn signal switch failure. On GM vehicles with a multi-function turn signal switch and combination stop/turn/tail lights (all rear lights are behind red colored lenses except for back-up lights) The brake light power is routed through the turn signal switch. This makes it possible for the right rear light to function as a stop light while the left rear turn signal flashes, and vice-versa. When the contacts fail to remain constant the brake lights, and turn signals can become intermittent. The proof that the brake light switch is functioning correctly is that the high center (cyclops) brake light functions properly. Wiring integrity is verified if you can prove that turn signals operate, but that can still be intermittent with this complaint, BUT if you use your hazard switch to turn on all the signals at once, you can verify wiring integrity. This is because the turn signal, and the brake light use the same circuit, and bulb filament in the rear lighting assembly. If any Hazard lights fail to function, check bulbs first, then retest. If all Hazrd light flash correctly and reliably, bulbs, sockets, and wiring have proven integrity, and the turn signal switch is the remaining component in the system which needs to be tested. Unfortunately, this switch requires disassembly of the steering column for service, testing or replacement. If you have never disassembled, and successfully reassembled a GM tilt steering column, I would reccommend professional assistance.