Back brake lights at bottom does not work only the one top light

the brake light switch is located in top part of the brake pedal and it controls all brake ligts the top and bottom lights use diferent power line, both come from brake light switch.

You may have a problem with the turn signal switch, as power comes out of that switch to power the brake lights, the high mounted brake light does not go through that switch.

Some of these had two fuses for brake lights. One for the top/center stop lamp and another for the rear left and right brake lights. Usually one said "stop" and the other said "brake" and one was in the underhood panel while the other was in the dash fuse panel. It's not uncommon to blow a brake light fuse [LR and RR] if you tow a trailer but some of these had seperate fuses for the trailer lights also. If you have a test light check both sides of the two fuses for power [ignition key on] while stepping on the brakes. It should at lest narrow your search a bit.

bad wire.....

those two are not on the same circuit, start by checking fuses, bulbs, voltage at sockets, groungs at taillights and brake light switch on pedal

Check for a missing or poor ground connection to the rear lamps. Check for ground (0V) at each rear lamp bulb socket connection.

More then likely your going to need the turn signal switch, been the brake light circit runs through the switch.

Check for power out of brake light switch by brake pedal. Of its faulty , the 3rd brake light will still work. Hope this helps

the problem is probably your turn signal switch. I know it sounds weird, but the brake lights work through the switch. If the third brake light works, then the brake light switch works, the turn signal switch works the lower brake lights. It's the switch under the steering wheel inside the column...not the easiest or cheapest thing to replace, but should fix your problem. If you decide to do it yourself, tie some wire to the connecter on the end of the switch wires at the bottom of the column...that way when you pull the wires up throught the column, you can use the wire you tied to them to pull the new connector and wires back down through the column.

Upper brake light works fine, lower brake lights don't work at all, with CHECK BRAKE LIGHTS warning every time you step on the brake:

In the trunk, remove the fuse access panel on the drivers side.

The fuses are on the left, and on the right is a black board with a number of square, rectangular and flat (card?) switches that plug into the board.

On my 2001 S60 T4, there are four flat card switches near the top; one by itself, then a space, and then three in a row (see below):

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When I began pulling the bottom one out, the lower brake lights worked and the warning went out. If I re-seated it completely the problem came back, but if I wiggled it out just a bit the problem goes away.