If I bring my car with a check light on for an oil change the garage is going to charge me for the oil change but will read and reset the check light for free. But if I skip the oil change then it costs me $40 to read and reset the light. Doesn't it sound a little bit strange?

How are you going to give a free estimate for a repair if you are not going to diagnose what's wrong with my car in the first place?

In my experience I've never been asked to pay for an estimate even, in one case, it took 2 hours for a Honda dealer tech to determine the reason for rough idling. And the 2 hours they spent went directly to their overhead. But I brought the car back for the repair and been their loyal custumer ever since. But when I'm asked to splash $40 to read my check engine light code then I rather invest $122 and get the software to read it, or I just show up and ask for an estimate on an intermittent problem and they will reset the light for free, but there won't be much of a trust and customer satisfaction and loyalty.