I have read in this column that Harbor Freight has a good deal on scanners, and I see it's Cen-Tech brand. I also see Actron scanners advertised. Since the Cen-Tech is only $39.99 it's more attractive, but is it really a bargain? Also Harbor has another model for $79.99. I can't find any consumer info about the Cen-Tech. And then, Auto Zone will check it for free; should I just use their service and forget buying one?