Warranty & CEL's question

[S.F.W.]

Situation - I have an '04 Mazda 3, currently has ~127K, and is covered by MAP until 160K. Recently, I have been seeing an intermittent Check Engine Light pop up. Since it really has not been an issue, I figured I would have it diagnosed at my next oil change(which I need shortly anyway), since I still have my oil changes done at the dealer.
Called the dealer yesterday to book an oil change for next week, also wanted to have the CEL diagnosed. The dealer informed me, that there is a $99 dollar charge to diagnose the CEL. I replied, that the car is under warranty, and was told, unless they are able to make a warranty claim for a repair, I would be charged the $99.
This has me confused...why am I being charged a fee for diagnosing a problem with my car..when my car is in warranty?

I should also note, I have been given this same explanation by two separate dealers.

[m_bisson]

yep... that's how warranty work is done. If they diagnose it and find something that isn't covered by warranty they will waive the $99 and just charge you the cost of fixing it.
I'm very weary about the MAP... It doesn't cover "leaks." So if the roof leaks, or water is pouring in the windows, you're not covered. Why would that NOT be covered? Is it something that happens often enough that it costs them too much to cover it?

anyways, different places charge different fees to inspect different things. There's no way around it, except to try somewhere else for a cheaper price.

[Donutz]

I get my CEL's pulled for free. I'll PM you.