Security light is on, wont start

Year make model.
Some cars have security chips in key, around ignition switch, or around gear shifter. If your cars security light stays on and wont start something in 1 of those 3 keeping it from starting.

check that it has power at the coil ,crank sensor,etc. with a test light when cranking it over.

When the light is on, the security feature of immobilizing car-wont allow starting-is active. Pretty difficult and time-consuming to permanently disable the security system, but some have figured it out and published their research over the internet. If yours gets worse, if the light stays on more frequently, you may want it permanently removed. I think it was a ruse by GM and car makers to add cost, and cause more frequent repair visits, but that just me.
Google "disable vehicle security system" or some such, to see results.

Do yourself a favor. Take it to a shop that installes the systems.

The security system is shutting down your fuel pump for some reason.Have the car checked for security codes.

sounds like you need a new ignition switch the pass lock is screwing up common.

With the new lock cylinder in it, turn the key on. The security light should blink. Leave the key on for 10 minutes, the security light will quit blinking and go out after 10 min. This will reprogram your security system and the car should start. Also leave a battery charger on it while the key is on, If the battery goes dead during the 10 minute reprogram sequence, you will have to start over again.

when u see the security light blinking and it wont start u simply turn the switch on and leave it on till the security light stops blinking then turn the switch off and start the car up

if the security light is on it could be the ign lock cylinder, it has two small wires attached to it and one may be broken and are the keys the ones that came with the vehicle