My horn and light dont work and my trunk doesnt

THAT IS ODD UNLESS THE TRUNK HAD BEEN OPEN/ CAR SITTING & WEAK BATT DRAINING W ELEC SHORT. NO PUN INTENDED! OPEN THE TRUNK & TRY AGAIN., DONT THINK IT WILL, BUT IF NO START CK BATT CONN , BOOST.& HAVE BATTERY ,ALTERNATOR CHECKED ALONG W/ PROPERLY HAVING IT CKD FOR ELECTRICAL SHORTS. if IT WAS SITTING AROUND A WHILE WITH THE TRUNK AJAR,CLOSE THE TRUNK BOOST IT, RUN IT TO RECHARGE THE BATTERY BY ITSELF (20MINS) SHUT IT DOWN, RESTART CK LIGHTS,HORN, ETC. ALL WELL YOU GOOD TO GO. NO START AGAIN THEN THERE'S AN ISSUE W/ THE BATTERY & POSS AN ELEC SHORT.. GOOD, FRANK M

One of the circuit has shorted. Do this replace fuse open trunk with key disconnected trunk mechanism try horn and see if fuse blows if not the trunk has shorted. If it blows the horn has shorted

My car has a fuse box near the battery. when you take the cover off there is a map under the cover to show what all the fuses and relays are. I would check the fuses.

Either via an actual theft attempt or you (or someone with your keys) not realizing that you/they actually armed the vehicle and opened the door or trunk afterwards.

Essentially this sounds like the vehicle was entered after being armed and the proper precedures not met to reset it.

The car may just need to be locked from the outside with the key (not the remote or keyless entry) while the doors are closed and windows are up, and then also unlocked with the key...

However it sounds as though you have perhaps driven it since then. If this is the case

You may want to check all your fuses and replace the ones affected by the anti theft system.
Security - Pwr Locks - Horn - Pwr Trunk Release _ Int Lights - and maybe The Emergency Flasher as well.

Be sure and check under the Dash, Hood and under the Back seat.

Cadillac recommends after a theft attempt, the vehicle may need to be serviced. So I recommend going through the fuses first, even replacing the battery in your remote fob and then if the problems still persist. have the vehicle serviced.

Good Luck and Happy Motoring

Respectfully

there is a problem with the trunk latch if your rear seats fold down use light to see if latch is jammed if seats dont fold you will have to remove rear seats you might want to see how much a shop wants this can be a tricky job

go back the trunk put the key in and turn it resets the system worked on mine found it out googal
i keep take the battire off and didnt work it go off when it get hot but this works the trunk are turn the key resets it strange

check fusebox you may have blown the fuse

The horn and the flashers are controlled by the 15 amp HAZ-Horn fuse.
The trunk light is powered by the 20 amp Dome light.
The radio is powered by the above Dome fuse, and the 15 amp Radio & CIG fuse.
With a 12 volt testlight, check for power on BOTH sides of the above fuses. If you have no power to either side of the fuses, you have an open circuit under the hood that feeds said fuses: Look for an open circuit in the main fusible link coming right off of the battery positive terminal to the wiring harness.

buy a new car

check all fuse are normal , if damage change it first other wise
you have reprograme the remote with car or change the door control switch