Hello my key turns but wheni try to start my car nothing its completly dead then a security flashes because all the lights come on if i left it sit for like 4 hours it starts agian. i thought i was my aftermarket alarm but they said it wasnt. I have no clue what the issue is?? this is the third time this week this has happened help me??? Elena

Resetting the Passlock system should fix it. If it doesn't you need an auto electrician or an auto locksmith.

https://www.google.com/search?q=2001+gmc+yukon+security+system+reset

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I'm not a car mechanic, but, it sounds like you might want to check the fuse to the ignition switch, and, if that fails, it might be a problem with the Start Safety Switch on the transmission. Good luck.

Battery is corroded, clean it and charge your Battery... Then see what happens...

A dead battery will not start a car

Very interesting site here.. regarding your problem. http://vatspasslockpasskeysecurityhelp.yolasite.com/
Another thought.. even though you charged the battery, it's not at all uncommon for a car battery to be very damaged by fully discharging. Especially if not new-ish. One or more cells in it may be bad causing the overall voltage to be under normal. This alone can cause the problem you have. I would try jumping it with another car or test the battery to see if it's got at least 12.7 to 12.9 volts when sitting doing nothing. Good luck.

The most likely cause of the problem is that your security module is not reading your key correctly. This is usually due to a defective key tumbler assembly. Try this to get it started:

1. Connect a battery charger or connect to another vehicle with jumper cables to keep the battery from running completely dead. If you set your parking brake before turning the key on, this will also help because it will keep your daytime running lamps from coming on.

2. Turn the key to the RUN position and wait about 10 minutes until the security light stops flashing.

3. Without turning the key off, turn the key to the START position and see if the engine will start.

If this does not work to get it started, you will have to tow it.
In either case, (whether you get it started or not, the key tumbler assembly probably needs to get replaced.

you need to get a new ign. lock cylinder and chip key. Or you can get a lock cylinder and copy your old key with a regular key no chip. Take new cylinder, put old chip key in it. Plug into harness at the bottom of steering column just behind the dash, fine orange wire from existing one in the column. Hide lock cylinder under dash and start car with copy of old key.

Next time check to see if the security light is flashing. If it is then you set off the system.Some models the security is set everytime you leave the vehicle. I believe yours can be changed thru the radio, check your owners manual. If the security is set off, turn the key off, then bck on, let set for ten minutes, you will have to do this three times, do not take the key out or try to start it untill after the third time or you will have to start over. If the security light is not flashing then you have a ignition switch problem. The switch is locate under the dash mounted to the steering column. not to hard to replace.Let me know I can help, If you need it.
Randy

im just gonna take a stab in the dark here i understand that your security light is on try unlocking your door with your key sometimes you just need to reset the security. otherwise ive seen a security module go bad that may be preventing you from starting it.

sometimes turning the ignition on 3 times quickly without starting will reset the computer. If the van has power locks and keyless entry then try using only the keyless entry. Sometimes your car wont have a alarm but an anti theft device which will not allow it to start if it goes off or something triggers it.

if the security light is on leave the key in the ignition in the run position for ten minutes untill the light gose off or starts flashing make sure its the factory key or else it wont work