Question about 1999 GMC Suburban

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1999 GMC Sub won't start when "Security Light" is Flashing.

1999 GMC Sub 86K miles. When you turn the key to on, if the security light is flashing, won't start, but turns over. If you wait 20-30 min., it starts right up. This occurs randomly. Could this be related to Key Fob battery? Otherwise it runs like new, built in Wisconsin plant.

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  • wsiebert3 May 26, 2009

    This only occurs, maybe once in awhile, it'll go 5 weeks without happening, so I doubt if it's a wiring problem. Do you know anything with regard to the "Security" light on instrament panel. What triggers that? Is it somehow sensitive to the unlocking/locking of the doors with the key fob?

  • wsiebert3 May 27, 2009

    The idea with the alcohol sounds worth trying. About the theft mode, it usually starts in 20-30 minutes on its own, without doing anything.

    I took the key fob apart and checked the batter with a meter. Battery is fine, but on the inside of the fob housing, it says: To Reset: Press Lock & Unlock at the same time near the vehicle?? Do you think it would need programming if I did that??

    Thanks for you help with this!!



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If the security light does not flash after you start the engine and it stalls, then security is not the issue. This sounds like there is an issue with fuel supply. I would first start with the fuel filter. Just to be sure about the security reset

30-Minute Learn Procedure
1. Turn ON the ignition, with the engine OFF.
2. Attempt to start the engine, then release the key to ON; the vehicle will not start.
3. Observe the SECURITY telltale. After approximately 10 minutes, the telltale will turn
4. Turn OFF the ignition, and wait 5 seconds.
5. 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™ Sensor Data Code and/or passwords
on the next ignition switch transition from OFF to CRANK.
Important: The vehicle learns the Passlock™ 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.
6. Start the engine. The vehicle has now learned the Passlock™ Sensor Data Code
and/or password.
7. With a scan tool, clear any DTCs if needed. History DTCs will self clear after 100
ignition cycles.

check with this link

Good Luck

Appreciate to rate as "Fixya"

Posted on May 27, 2009

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That the most common problem with this is that there is a wiring problem that has either shorted out/disconnected or the ignition system is just not reading the "chip" in the key itself and it may be in need of repair or the battery is got weak in the key.that needs replacement.
as this are most common reasons for this problem.but as you said other then this it runs fine so i doubt on the ignition system not reading the key or the battery in the key fob got faulty.
it has to be checked.this will help you.
thanks.please do rate the solution.thank you for using fixya.keep updated.

Posted on May 26, 2009

  • spark9 May 27, 2009

    if the wiring is not proper the problem will be whenever you start it will not start directly.but in your case its it must be related to key fob.

    when ever you face this problem at that time instantly take some rubbing alcohol on paper towel and clean your ignition key, see if that works.keep the rubbing alcohol available with you.


    also it can be possible that vehicle has gone into theft mode . To release from theft mode put key in on position... leave on for 1/2 hour, take key out for 5 minutes then will be released.


    click this link directly and read the conversation for more help

    keep updated.



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