Changed the ignition cylinder and the switch as well.. engine starts then stops.. how can i bypass the security system to turn off so that the new key will work ?

What is your question?

I changed out the ignition key cylinder as well as the switch itself.. couldnt reprogram the new cylinder due to the numbers on the brass tumblers being worn and unreadable.. How can I bypass the security system so that the new setup works and let's throw engine continue running for more than 2 seconds ?

How long has your 2000 Jeep Grand Cherokee had this problem?

2 days