Hey was wondering if there was a way to for hidden CEL to turn on? Reason being:

I had a CEL with 2 codes.
Car died and had to switch battery
Car restarted with no CEL

2-3 weeks of driving later, went to smog and passed CA test (where having a CEL auto fails)
but the CEL started showing again right after (i'm assuming something happened during smog that forced it to show up and luckily the guy was nice enough to let me pass)

but any idea of how to force it to show? i have some ideas of how to fix it, but would like a quick way to check.

thanks!
Tony

 

You cannot force a check engine light on.

Check for codes yourself or have the car checked at autozone.
See the 4th gen section stickys for instructions on how to read the codes yourself.

 

I know how to get the codes, so that means the codes will always show regardless whether the CEL is on or not?

 

The code will show as long as the problem remains.