Security light stays on - 2004 Chevrolet Impala

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.

The Passlock system temporarily lost contact with the key

Alternator will keep engine running when battery becomes disconnected through a loose or corroded connection.

Here is a link that has alot of info on the security light.

http://vatspasslockpasskeysecurityhelp.yolasite.com/

Looks like the TDM in the security system (VATS/PassKey) is having problems, it's typical on those cars. You can find a great write-up here: http://newrockies.ca , it was the only thing that saved my Park Avenue.

The security system (VATS/PassKey) is having problems, it's typical on those trucks. You can find a great write-up here: http://newrockies.ca , it was the only thing that saved my Park Avenue.

if you have a spare key try that sometimes a worn key will trip the security

You need to reprogram the security system. Hook up a battery charger. Turn the key on, the security light should flash. Leave the key on until the light stops flahing.(11 minutes) Turn the key off for 20 sec. Turn the key on, do the same thing a second time, turn the key off. Turn the key on. Do this a third time. After the third 11 minutes and the light is off, Start the truck.

For the security light you need to replace the ignition lock cylinder or bypass the security system. For the other two, you need to have the car scanned to see what codes are in the ecm and the abs module.

First place to check would be a fuse.  See if there is one labled security or alarm.  If there is try changing that.