How do I reset the computer

Hi

You can try disconnecting the battery for 5 minutes and then seeing if this resets the immobilizer.

Let me know if this does not work and we can try something different but this is the most likely easy correction.

Thanks

https://www.2carpros.com/articles/how-to-reset-a-security-system

Hello,
  Thanks for your advice. I unplug the battery and start, it runs fine. But I turned it off and turned it back on, it didn't work again. How can it be permanent without removing the battery?
  Thank you!

It must be the key you are using. More than likely it has an issue. I think on these older Jeeps, you had a courtesy start which means it lets you start it one time to get it the shop or home and then it disables again.

You said you had another key. Does this key work to start the vehicle?

Thank you,
Both keys are still in normal use, when I replace the ECM, those two keys only start up once.

When this does not start, does the theft light blink? Try the attached procedure and see if the lamp flashes. If not, this indicates we have an issue with the system and will need a scan tool that can communicate with the theft system.