Q: Why can't my check engine light come on after starting the car?

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My service engine soon/check engine light comes on like it's supposed to when the key is in the on position. Meaning the light isn't broken. The problem is that the light NEVER comes on while the car is running. Most people would probably say "just leave it because now you won't ever get the annoying light", but I'd like to know if something is wrong. It used to misfire, no light or codes, I take off the air intake completely, no light or codes, I spray enough carb cleaner into the throttle body to almost make the engine cut out, still no light or codes. At this point I have the suspicion that the previous owner may have tampered with the computer to the point of having the light only come on duringredients the on position but never anytime else. Thank you very much and I hope we can fix my issue.

My car has 154000 miles.
My car has an automatic transmission.

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