Anti theft system light on at odd times wont let my car start?

Hey JROLEMAN,

This system cannot be bypassed. The #1 reason for a security problem is the drivers door latch. What happens is the switch inside wears out causing the alarm to think the car is being stolen. Replace it with a new one and the problem should be fixed.

Here are some guides on how to check it.

https://www.2carpros.com/articles/how-to-reset-a-security-system

and

https://www.2carpros.com/articles/how-to-check-wiring

Also there are two small wires up by the ignition switch that break causing the alarm not to reset.

Please let me know what happens so it will help others.

Best, Ken

30 Minute Learn Procedure
Tools Required: None
Turn ON the ignition, with the engine OFF.
Attempt to start the engine, then release the key to ON. The vehicle will not start.
Observe the SECURITY telltale, after approximately 10 minutes the telltale will turn OFF.
Turn OFF the ignition, and wait 5 seconds.
Repeat steps 1 through 4 two more times for a total of 3 cycles/30 minutes. The vehicle is now ready to relearn the Passlock(tm) Sensor Data Code and/or passwords on the next ignition switch transition from OFF to CRANK.
IMPORTANT:The vehicle learns the Passlock(tm) Sensor Data Code and/or password on the next ignition switch transition from OFF to CRANK. You must turn the ignition OFF before attempting to start the vehicle.

Start the engine. The vehicle has now learned the Passlock(tm) Sensor Data Code and/or password.
With a scan tool, clear any DTCs if needed. History DTCs will self clear after 100 ignition cycles.

The dealer should not have disabled the theft system. If car was stolen due to a disabled theft system, the dealer would be responsible. I doubt insurance would pay if the security system was intentionally disabled.

Take it back to dealer and have them repair it.

There is a procedure for reseting the system:

Turn key on
security light flashing
try to start and let go leave key on
security light flasher for about 10 min
when it stops
turn key off and start car
key needed to be reprogrammed
happy driving after that
in some rare cases you may have to do that 3 times total of 30 min.

However if an aftermarket remote start, then that could also be the problem.

TRy this turn key to start let go then turn to ACC position THEFT light should be on and start to flash. it takes 10 mins. light will stop go off then start car.

This guides show how

https://www.2carpros.com/articles/how-to-reset-a-security-system

Try resetting anti theft. If it doesn't turn off the drivers side door latch needs to be replaced in most cases.

It can be a module going bad for the anti theft.

Do you have a crank but no start or it doesn't turn over at all? Is the antitheft light on solid or flashing? I ask because the low battery on that car shouldn't trigger the anti-theft.

Hello, I'm Danny.

Lets try an anti-theft, security system reset first. Here is a link to the tutorial:

https://www.2carpros.com/articles/how-to-reset-a-security-system

After reading, Scroll the page to find Chevrolet. Get back to us after performing this and we'll go from there. Hope this helps and thanks for using 2CarPros. Happy Holidays.

With no anti-theft and no crank it's not the anti-theft system. On that GM the anti-theft turns off the fuel pump and will let the engine turn over and start but it would run for about 2 seconds the shut off. From then it would still crank but won't run. In this case I suspect that one of the battery cables is corroded and the power isn't getting through. When you turn on the lights do they come on? When you try to start it do you get a click or nothing? I would start by having the battery tested, if they go dead for long they can short internally and will not provide power enough to start the car. Many parts stores will do that for you for free. Then I would check the cables over for corrosion, The GM side terminal batteries tend to seep acid that goes into the cable connector and eats the internal metal until they stop working, but because it's all under the insulation you cannot easily see it without digging into it.

https://www.2carpros.com/articles/everything-goes-dead-when-engine-is-cranked
https://www.2carpros.com/articles/symptoms-of-a-bad-car-battery

If you have a spare it's a place to start, but I would also check those cables, the side terminals are very good at failing.