I figure this'll be a fun discussion . . .
I'll get it started, now
At the shop I work at, I'm the only one doing the smog inspections at the moment . . . that includes dyno smogs, two-speed idle, and the plug-in test for newer OBD2 vehicles
Anyways, one of my coworkers, who is a little younger, has been shadowing me lately, watching me do the smog inspections, and asking the occasional question. I explained everything I'm doing, what I'm looking for, etc. I even showed him our state's bar website, and the how-to videos and inspection manuals, which can explain it better than I can.
A few days ago, everything was going fine on a Ford truck, which was getting a 2 speed idle test. Non-OBD2 and too large to go on the dyno, for those who are curious why it was getting a 2 speed idle. Anyways, I called him over and told him the truck was going to fail. He asked why. I said I was at the part of the test where I am instructed to turn on the ignition and observe if the check engine light came on. It did not. I had made sure to leave the ignition off for a few minutes for any pcm "timers" to reset . . . on some GM vehicles, if you have the car running, shut it off and immediately turn on the ignition, the mil will NOT turn on. But no matter how many times I tried, that mil would not come on under any circumstances on the Ford truck.
I explained that when I entered "no" on the computer, that would mean a failure, no matter how clean the emissions. And they were clean, as it turned out.
The guy . . . who's been wrenching for several years, and apparently even graduated from a for-profit auto program . . . asked me if I can't just enter "yes" and figure it out later.
I couldn't believe this guy was earnestly posing this question . . . !
I told him if I did that, there's a fair chance the guy who had worked on the truck earlier and asked me to smog it, hoping the truck would then be released, might tell the boss "I'm done with this truck and am ready for my next job"
Instead, I entered "no" on the computer, the truck failed, I filed away the printouts of the failed test and headed over to the boss's office. I told him that unfortunately the truck failed, because the check engine light did not turn on, and that when the other guy fixed the issue, I would retest it. The boss was not upset about the turn of events, I might add. I then found the guy who had been working on the truck and told him the bad news.