Why are there no brake lights or high-level stop light?

Do you know anything about automotive electronic's ? The brake pedal position sensor is a input to the BCM - body control module ,the BCM turns on the stop lamps . Possible short in the (CHMSL ) - center high mount stop lamps , wiring etc.... Causing problem inside the BCM . Do you know what wiring diagrams are ? Free one's here http://www.bbbind.com/free-tsb Enter vehicle info. year , make , model an engine size . Under system click on lighting , then under subsystem click on exterior lighting . Click the search button then the blue link's . First diagram show's the brake pedal position sensor input to the BCM ,lower right . Second diagram show's BCM power supply to the third brake light (CHMSL) . Having a qualified repair shop with a professional scan tool to check for DTC'S - diagnostic trouble code's could save a bunch of time in diagnosing the problem .
DTC B3903
The body control module (BCM) supplies voltage to the center high mount stop lamp (CHMSL) and the powertrain control module (PCM) when the stop lamps are active.
DTC B3903 Stop Lamp Relay Circuit

Stop Lamps
The body control module (BCM) is responsible for controlling the stop lamps. When the driver presses the brake pedal, the BCM will receive a signal from the brake pedal position sensor. The BCM then supplies battery positive voltage to both left and right stop lamp assemblies and to the center high mounted stop lamp (CHMSL). The stop lamps are grounded at G401 and G403. The CHMSL is grounded at G302.

Did you check STOP LP fuse 15amp. in the rear fuse block ? Do you know where this is. Fuse Block - Rear Under the rear seat, on the left side of the floor pan.
The STOP LP fuse in the fuse block - rear supplies battery positive voltage to the normally open stop lamp switch. When the driver presses the brake pedal, the switch contacts close. The battery positive voltage flows to the left stop lamp assemblies, to the right stop lamp assemblies and to the center high mounted stop lamp (CHMSL). The left stop lamp and the CHMSL have ground at G402. The right stop lamp has ground at G401.
Did you check for power at the stop lamp switch ? both in an out of the switch with brake pedal pressed ?
Did

Which fuse did you replace ? The one in the under hood fuse box or one of the two in the I/P fuse box . Do the CHMSL - center high mount stop lamps work correctly ? Here is a description how they work .
Stop Lamps
The STOP LP 25 A fuse in the underhood fuse block supplies battery positive voltage to the normally open stop lamp switch. When the driver presses the brake pedal, the switch contacts close and battery positive voltage is supplied to both the STOP 15 A fuse and the CHMSL 10 A fuse in the I/P fuse block, and to the turn signal/hazard module. The turn signal/hazard module then supplies voltage to both of the trailer rear turn/stop lamp supply voltage circuits. The voltage from the CHMSL 10 A fuse is to the center high mounted stop lamp (CHMSL) and the trailer jumper harness. The voltage from the STOP 15 A fuse is to the stop lamps, throttle actuator control (TAC) module, and the cruise control.
Does yours have trailer light hook up ? If so check trailer wiring connector for corrosion . Also check the turn signal / hazard module .
Does

High level brake light is connected , in parallel with, all other brake/stop lights.. It is not on a separate fuse, so, check, or replace the other stop lights.
Or could be a bad ground on brake lights, but not on high level light.

Check fuses first. Should be a fuse labeled 'Stop' or 'Brake'.

If fuses are good, climb under the dash and look at the brake switch, it's high up on the brake lever. Make sure it is operated by pressing in the brake pedal.

If none of your brake lights including the 3rd or high mount light are not working.You will need to check fuse no.13(20amp) in the under dash fuse panel,then check for power to the brake light switch on the top of the brake pedal.You should have power on the light green/red wire then when you press pedal you should have power on the light green wire also. If the 3rd light works but not the other brake lights then your problem will be the multi-funtion switch(turn signal switch) or the wiring from there to the brake lamp sockets or the bulbs themself. If you need further assistance please let me know. If this helped you then please feel free to rate the solution accordingly. Thanks, Midwest-tek

Seems to me that the brake lights switch has a problem there is a way to test this problem, you normally press the clutch pedal and hold down the start button to start the engine, now try pressing the break pedal down and hold the start button, if the car does not start up change the brake pedals switch.

You have a ground fault somewhere, check all the grounds for the lighting.

hi assume all brake lights including high level light ? are not working ? 1st check is the fuse ? if it is ok? then next check is the brake stop light switch located at the pedal just near the top of pedal the switch is normaly adjustable and screws into the pedal boxframe that pedals fit /pivot to the switch operates on plunger method ie when pedal pressed the small plunger moves out and puts lights on then when pedal released plunger is pushed back lights off the switch is plastic and has a plug with 2 wires attached to test if plug is defective ? unplug wires from switch then using either a paper clip or piece of wire ? connect /join both wires in plug then sitch ign on if lights work ? switch is defective simple diy to replace cost here in uk for switch approx £4 hope this helps ?

Check the switch that comes into contact with the brake pedal arm. Run your hand up from the pedal itself to the first thing you feel-it's most likely the switch. With the car running-in park- press the button on the switch that touches the arm the pedal is attached to. If the lights come on-then adjust the switch ( if I remember right this is done by turning the nut that holds the switch). if they don't come on-replce the switch