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Q: Van won't start, anti theft security light is on. It starts but it won't hold. on 1999 Chevrolet Express 3500

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How can I deactivate the security system on my vehicle? I replaced the computer on the van and the security light came on and now it won't start.
No car image 94a1663db56199c5353592009e34aaa51078a2469bed068bb8d6f0ba43accf97
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try to start car & let key go, do not turn key off. wait for security light to go out. then turn key off & do same thing 2 more times. on the fourth time start the car. make sure battery is good or have charger on it. good luck...

Sounds like the pass key sensor is going bad. GM has an issue with these as they only last about 10-15 years. Depending on which version you have it reads a resistance from your key through and shuts down the fuel injectors. You might want to check that out as I have the same issue with a 2000 silverado and just have not purchased it to replace. Sometimes you can leave the key in the on position for about 10-15 minutes and then try to start it. You can disconnect the battery for about 10 minutes and then reconnect and try to start it. I have recently found that you can set off the security alarm while inside then use the key in the ignition to shut it off and try to start it as well.
Hope this helps
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