This. I went to get an inspection at a Valvoline place and the final part involved plugging their device to the car's computer. They were clear that it had nothing to do with the inspection, just "policy". I didn't push back since it was the last day for inspection,
but honestly. Our culture keeps is of isolation and siloed personal lives, except for corporations, they have their fingers in the details of all personal affairs.
It is worth noting that pretty much all the "quick oil change" brands have horror stories associated with them. Everything from minor ("they didn't notice my air filter needed replacing") to fraud ("they tried to get me to pay for an air filter that was replaced the week before; and showed me a dirty one that wasn't mine") to outright dangerous ("they left a tool on my engine that could have (or did) destroy when it fell into the workings, later" [1]). As a general rule, they tend to hire people without any _real_ training or motivation to be good at their job. I highly recommend being very wary of such places.
To be clear here, not all of them are like this; possibly not even most of them. But enough of them are that I generally try to always go to a local shop to get my oil changed. It's not worth the risk to me. If you have one that you know enough about to be comfortable with, none of this applies to you.
[1] I had this happen to me. Got home, popped the hood, and there was a screwdriver sitting on top of my engine. If it had fallen in on the highway, it could have caused some serious damage/injuries. Luckily, it didn't.
I would also recommend looking up the procedure for changing the oil and doing basic maintenance on your car! On most modern cars it is very easy, and then you can trust it was done right.
Honestly, as someone who's been involved with designing some of the internal systems and seeing how effective they can be, the large majority of the time a car either has the potential to be able to detect or already knows where the problems are located. The facilities to detect that are simply not in place or exposed to end users/techs in enough detail.
"emission readiness" is a specific state of the computer where all of the sensors are reporting "good for an extended period of time". It takes several drive cycles to get into that state. So that you can't, for example, reset the ECU and drive in for an inspection right then.
They do also do live tests with a sensor, but the "ECU says car is emissions ready" is an additional requirement. At least in many US states...maybe not yours?
> all of the sensors are reporting "good for an extended period of time"
Not exactly. Boring monitors like those for sensors or actuators are excluded / always reported as ready. Even misfire is always ready, and fuel was, too, until recently.
But of course since the more intersting monitors take long to complete, when they do reach ready, simple sensor checks would long have set at least a pending code if there was a problem.
Next update in california will likely require all monitors to be included in the readiness status latest for model year 2027.
Hrm. I've done this myself with the OBD-II reader and some do come up pretty quickly, but they took all some amount of running/driving to be ready if you reset the ECU...which people would try if there's a code stored / check engine light on. Some of them take quite a while to be ready.
