At Wal-Mart just go with the cheapest one that says it'll read the code and turn off the check engine light. As I recall, the most expensive reader had all the generic codes in memory and showed what they meant on a small display screen. So with the cheap one you have to look them up yourself in a booklet. No biggie. You find the Isuzu specific codes online, print 'em out, and carry the list in your glove box. Some of these Isuzu's throw codes like every ten minutes (obvious exaggeration).

Mark