Service security system light comes on and security light stays on. Doesnt happen all the time.

This is a very common problem on GM vehicles. The security system is known to fail. Basically when you insert your key, the system looks for a code from your specific key. If the system cannot get the correct signal from the key to the theft module, it assumes the key is incorrect and goes into SECURITY lockout mode. (prevents hotwiring) This has been happening with GM's for a very long time. There are ways to bypass this now. Read through this page for info, solution as well.
http://www.diy-gm-security.com/

This is a very common problem on GM vehicles. The security system is known to fail. Basically when you insert your key, the system checks for certain OHMS resistance. If the system cannot get the correct signal from the key, it assumes the key is incorrect and goes into SECURITY lockout mode. (prevents hotwiring) This has been happening with GM;s for a very long time. If the light comes on, but you can still start it, thank the lord. Failure is coming soon. There are ways to bypass this now. Read through this page for info, solutions as well.

http://www.diy-gm-security.com/

This may be the dreaded antitheft security system. Look for a picture on the dash when this happens that says SECURITY or a picture of a car with a lock through it. This a visual indication that something in the car's antitheft system is failing. In most GM cars and trucks there is a hidden system that most people are unaware even exists. From the moment you put your key in the ignition, there begins a constant line of communication between your key's security chip or transponder, to the ignition's lock cylinder, and then to the car's TDM (Theft Deterrent Module). These 3 parts are in CONSTANT communication. If the key is in the ignition, then these parts are sending signals to each other.
The security light illuminates when that signal gets broken, or not seen at all. When the communication breaks, the car misinterprets this as an attempt at theft and goes into antitheft mode. (like it thinks it's being hot wired) The car shuts down because it is not getting that signal from YOUR specific key. This is why the security light turns on and shuts down your vehicle. It will either turn off the starter, or the fuel injectors. The vehicle may run for 2-3 seconds before shutting down. This link explains it pretty well.
http://www.diy-gm-security.com/

Two things will cause this, both are shorts in computers. One is the body control module, which stores the security system. The other would be the instrument panel. My guess would be the IP. usually when it happens with the BCM, the vehicle won't start. As long as it doesn't drain the battery, I wouldn't worry about it.

if it just shuts off, try the auto shutoff relay box..it may be loosing connection with the rest of the harness..

i had a similar problem with 2007 focus,car stumbled couple times,stopped at store for milk, car wouldn't start back up,alternator light blinking erratically.wound up replacing alternator,actually had the old one repaired,shorted diode.bad job was removing it from car.came out from underneath.

85% of the diesel engine problem is the fuel system. and rest 15%, if met, is a major problem. you have to check the filter. and make the fuel line solid. means no air in the system.

Call your local GM dealer and they can give you the procedure to reset. Also sounds like you knocked a wire off of the system.

Does it have a security system? If it does see if the security light is flashing. If it is you can reset most cars by turning the ignition to on and waiting for the security light to go off. Then it will start. This will happen again.

Just a wild guess.

go back the trunk put the key in and turn it resets the system worked on mine found it out googal
i keep take the battire off and didnt work it go off when it get hot but this works the trunk are turn the key resets it strange