Happens way more often than you might think. We even get sales calls asking if it will fix their car..... people who think VCDS is a professional tech in a box. Well, we're good, but we ain't that good.
Yes, that is always a funny conversation with the customer.
Them: [over the phone]: This light on my Jetta TDI is on, can you tell me what is wrong with my car?
Me: no, we will have to plug our computer into your car, and see why the light is on, then find out what is wrong with the car.
Them: yeah, but that computer tells you what is wrong.
Me: no, it tells me why the light is on.
Them: oh, so you just need to turn the light off? I can do that.
Me: no, the light is on because there is a problem, the computer allows me to see why the light is on, to afford me a starting point in diagnosis of the problem.
Them: but the car runs fine!
Me: yes, I'm sure it does, but the light can come on for many reasons and the computer in your car that makes the engine run is smart enough to be able to motor on even with a fault.
Them: well of it is smart enough to motor on, then why does it not just turn the light off by itself?
Me: because the car cannot fix itself, it can only alert you that it is having a problem.
Them: but it runs fine!
Me: [facepalm]: yes, but it may not continue to run that way, or it may have a fault that will cause poor emissions, poor fuel economy, poor power, or more.
Them: well it does seem to be slower now.
Me: oh, so your definition of "fine" is used on a sliding scale?
Them: well, it starts and moves. And hey, if my car already has a computer, why do you need yours to connect to it?
Me: well, actually your car has several computers, but none of them can print out what ails them, and some cannot even alert you via a light.
Them: you mean there are more lights?
Me: yes, many.
Them: where are those?
Me: [facepalm... again...]: all those red and orange lights that come on when you turn the key on.
Them: oh. Well, I also have this vibration. Can your computer tell you what that is?
Me: most likely not, I really need to see your car.
Them: for what, the light or the vibration?
Me: both.
Them: so how much will it cost to fix?
Me: I have no idea, because I have no idea what is wrong with your car.
Them: well I told you, I have a light on!
Me: [losing patience]: yes, but I need to have your car here, in the shop, for me to diagnose that!
Them: well, my sister-in-law said it is probably just a loose gas cap.
Me: [facepalm]: sounds like you have it licked then! Good luck! [click]