ok but like you say how you can know if the tool have 1 or 2 car left when you buy a used one... its hard to say and easy to lost your money... (sometime you find good person when you buy used but sometime you can find wrong person...)
cheapest model I see (I know its ebay but you can find good stuff)
Car fault reader code scanner diagnostic tool OBD 2 CAN | eBay
this:
V1 5 Super Mini ELM327 OBD2 OBDII OBD II Bluetooth Diagnostic Interface Can Bus | eBay
this:
http://www.ebay.com/itm/190606035926?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649#ht_2804wt_1056
or this:
V1 5 ELM327 Elm 327 OBD2 OBDII USB Can Bus Car Diagnostic Interface Scanner UK | eBay
thanks in advance...