Put new ignition in 2003 sunfire. engine wont stay running and theft lock symbol on in dash

What are you trying to say here light key on dash ? A symbol of a key light lit on the dash maybe . This would be a problem with anti-theft system .

Anti-theft system isn't allowing it too .
The Passlock™ System is provided in order to prevent vehicle theft if the ignition lock cylinder is forced to rotate or the ignition switch is operated while separated from the ignition lock cylinder case. If starting is attempted without authorization from the Passlock™ System, the powertrain control module (PCM) will disable engine starting. Start disable may be in the form of fuel disable or starter disable, depending on engine application.
The components of the Passlock™ System are as follows:
• The ignition lock cylinder and key
• The ignition lock cylinder case, including the Passlock™ sensor
• The ignition switch
• The body control module (BCM)
• The security indicator on the instrument cluster
• The powertrain control module (PCM)

Pontiac Sunfire Questions - car won't start - CarGurus

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CarGurusAug 16, 2011 - car won't start - replaced ignition lock on 2002 pontiac sunfire antitheft light is ... system goes into fail safe mode and you won't have any more problems. ...lock cylinder on 2003 pontiac sunfire....when new lock cylinder was ...

MAKE SURE YOUR BATTERY IS CHARGED OR NEW. TAKE OFF THE STEERING COLUMN COVERS. PUT THE KEY IN, NO EXTRA KEYS HANGING FROM IT. START THE CAR. UNPLUG THE CONNECTOR WITH THE YELLOW, BLACK, AND WHITE WIRES CONNECTING TO THE PASSLOCK/LOCK CYLINDER, AND IT WILL CONTINUE TO RUN.TAPE THE CONNECTORS. REPLACE COVER. YOUR THEFT LIGHT WILL STAY ON/FLICKER. YOU HAVE DISABLED THE SYSTEM. NOW THE CAR WON'T CUT OFF WHILE TRYING TO START IT. SUMMARY: YOUR PASSLOCK WAS FAILING. OTHERWISE IF YOUR IGNITION SWITCH WAS FAILING, IT PROBABLY WOULDN'T TRY TO START. FOUND THIS ON A SITE FOR A CAVALIER...... AND SUNFIRES DIAGRAMS AND THEFT FEATURES ARE MOSTLY THE SAME. NO PELLET IN KEY. NO RESISTORS. NO CUTTING WIRES. NO 10 MIN RELEARN. HOPE THIS HELP.

The problem is in the ignition cylinder lock.
The body control module (BCM) is what controls the theft deterrent system on the 2000 Pontiac Sunfire.
It can be reprogrammed, but is complex to do.

Here are some pictures for you.
http://www.autofuseboxdiagram.com/4232-2000-pontiac-sunfire-2-2-fuse-box-diagram/

http://www.automotix.net/usedautoparts/2000-pontiac-sunfire-chassis_computer-inventory.html?fit_notes=e1360a49a192739e006f059ad1d62904&seq_num=8

do u have an owners manual? this is the security system warning symbol, you have been locked out, try this reset procedure, if that doesn't reset the key code then you will need a dealer to hook up a GM scasnner and see what the problem is.
PASSKEY LOCKOUT RESET GM CARS 1999 UP
1) Put the key in the ignition and turn to the "ON" position. Leave it that way for 10 minutes. After 10 minutes turn the key and take it out. Repeat this process (2) more times (3 times, 30 minutes total) This should reset the PASSKEY system to recognize your key.

Check your chassis ground strap. There should be a braided cable, or a cable similar to your battery cable, that runs from somewhere on the engine to the chassis. The reason you have multiple items lighting up or working when you try to operate one item is because it is trying to get a ground through another source.

on a similar problem i had occured it is the theft lock that GM uses. You have to put the key in the ignition turn to ACC wait ten minutes and turn it off. You MUST do this three times and then the theft lock will turn off. Once that is out of the way it SHOULD start.

tryy replacing the fule injectors and the fuel pump could possibly be shot as well. you have a fuel problem.

Hi,,,
Theft sensor is Part of the Ignition Lock cylinder. On your Sunfire.

If you have problem with the theft system on your car.
First check the proper funtionallity of the Ignition lock cylinder.

if you Can explain me a little bit of your problem I can help you.

Thank you for use fixya...