Back lights dont work - 2005 Cadillac CTS

If none of the lights in back work, it sounds like something happened to the main wiring harness. Which is probably beyond your ability to repair at home.
If the parking lights and turn signals work in front you know the fuses are good, so they should also work in back.
The parking lights, turn signals, back up lights and brake lights are on 4 different circuits.

find the short, could be in the switch or a wire itself...and if you have a bulb out it complicates finding it even morenew fuse it, then turn things back on one at a time...should tell u where the problem is

it can be the bcm. body control module. it is located under the dash right next to the steering coluum

This make is not sold in the US so have no info on it. Sorry

The heater control panel is sealed so you can not access the lights. They simply go out and you have to replace the panel to get lights back.

CHECK FUSES AND GLOBES OR THERE MAY BE A PLUG FROM FONT TO REAR ALONNG THE KICK PANNEL THAT HAS CORODED

assuming you have brake lights and marker light, I would check the socket for voltage, both the contacts and probe the wire (Brown) for voltage...it could be a bad socket.... if no voltage, trace the "Bwn" wire back and keep probing til you find voltage, check the connector in the trunk on the LT/RT side also...hope this helps you...GL

Test the circuit board wires on the back side of your taillights where the bulbs go in to see if power is going there with the blinker on, if yes replace the circuit board (quite common with these trucks). If there is no power back there check your flasher relays for each turn signal, assuming they dont click off and on when you tip the turn lever. if all else fails, head for the multifunction switch behind your steering wheel inside the column that your turn signal/wiper/cruise control lever is connected to.

check for bloown fuse

did you check the fuse in your fuse box. just refer to your instruction manual. maybe the fuse got short.. hope this could help.