05 Cadillac will not start after spinning out on interstate.

Is the red security light flashing? No gas, could be fuel pump or a few other electrical issues.

https://www.google.com/search?q=2005+cadillac+cts+3.6+security+system+reset

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Will not start how ? Turning the key to start ,what happens ? Does the starter engage an spin the engine but won't start an run or nothing happens .

Won't start how ? When you turn the key to the start position does the starter spin the engine ? Or not ? This would be a no crank - no start condition ! Or when you turn the key to start the starter spins over the engine but it doesn't start an run ? This is a crank - no start condition . Both have very different diagnostic testing procedures ! An what won't say anything ? Is there a car an padlock symbol lit on the instrument cluster ?

should be a 15/16" socket and ratchet, they can be tight so you might need a breaker bar or a pipe on the end to get some leverage.

common symptom of worn ignition lock cylinder and key

probrably ignition key cylinder is failing n theft loc up the car

replace ignition switch electrical contact assy

I'd first try a different gas station... and make sure you're putting in premium if required. And also make sure that you get the gas cap on right... sounds stupid but it can cause problems.

If you are referring to the maker light on the fender you must remove the plastic wheel well liner panel section. from=nt of wheel well to access the light.