The code scan is free, sometimes people will ask you to plug it in and bring it back after it beeps, the plug is under the steering column on most vehicles, very rarely I've seen it on the passenger side, and some have it behind a small panel, otherwise the employee will plug it in for you if they have coverage for the counter. They will then print out a sheet with the codes, which are generally to be considered a path to the solution to your issue and not the solution itself.
They do free code scans. But all that it does is give you the codes that's causing whichever light to be on. And from that code they can print you out a list of the possible reasons why that light is on.
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