The Amazing Self-Repairing Car... maybe!?

Teri and I are entering our second year here in Nashville, and we had to get the vehicles smogged and cleared for emissions purposes. We had this issue in Los Angeles where Teri's 2000 Nissan Maxima would not pass the emissions test because a check engine light was on in the dashboard. We spent $600 to fix it, but in three days the light came back on. That was three or four years ago... the light has been on ever since.
So, we go to get our vehicles checked here, and mine passed again and her's failed AGAIN. Distraught, we took it into a mechanic for a diagnostic test and estimate on how much it would cost to fix it. After the test the shop said they could have everything up and running again for somewhere between $2500 and $3500 dollars. This was not good news.
A few days later, at our wits end, through prayer we decided to start looking for a new car. We didn't want to do this because we paid the car off and it was nice not to have a payment. So this morning Teri gets in the car to go somewhere and notices that the "Check Engine" light is off for the first time in four years. She then drives down to the testing facility and passes with flying colors!
What in the world!
So now we are left with a few thoughts. First of all, thank God for allowing us to pass the test and not having to plunk down a few grand in repairs. Secondly, we now question the whole smog test thing. I mean, with all the technology that we have at our disposal these days Teri's car failed on a technicality of a single Check Engine light. Once that light went off she passed. So it had nothing to do with her emissions, her cars fate was almost decided on a single light on our dashboard. That just seems stupid.