2006 XJ8L - KEY FOB DOESN'T UNLOCK DOOR OR ACTIVATE LIGHTS. DOOR KEY WON'T TURN EITHER DIRECTION

Lock mechanism is frozen. Thaw it out.

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you might want to check the fuse

It actually sounds like the micro switch in the drivers door that reads the key fob is bad, if the key works and the fob works on the other doors and the trunk. You will most likely need to have the door handle replaced, they're not very expensive by themselves but it can be a lot of work. Cadillac CTS Door Handle Repair Micro Switches Replacement 2nd Gen The video is a 2008 cts but will give you a good idea of whats wrong and whats required to fix it

Try reprogramming the fob. You can find videos on youtube

Close the doors. Lock the doors using the buttons on the key fob. Use the fob to again unlock the doors. The key should then work the ignition. If this will not work, you will have to tow your vehicle to the dealer and buy a new key and/or fob and have it programmed to the vehicle.

Your door lock actuator have issues

If the passkey is messed up, there will be a light on the dash that says security, or have a picture of a car with a lock thru it. If there is no light when the key is turned forward, then its NOT a passkey problem.

Sounds like you have a bad door lock actuator or one of the lock rods has come loose and is in a bind. Can you hear any noise from the door lock actuator in that door when you operate the power door locks? If not, you probably need to replace the actuator. The hardest part will be getting the door panel off without damage. Once the door panel is off, it should be fairly easy to replace the lock actuator even if it comes with the entire latch assembly.

the key fob remotes need to be reprogramed or have the battery checked... make sure to have all key fob remotes present when reprogramming...

weird this one, has a transistor playing up but where ??