Scan tool question

[T-ROD]

I have an Innova 3140 OBD1 and 2 scanner. My truck says it is OBD2 exempt on the valve cover so I am assuming it is OBD1 or some other diagnostics program. On the other hand I have a OBD2 style port on the passenger side, under the dash but it only has 5 or 6 pins in it and the other 10 or 11 holes are empty. When I hooked my scanner up to it using the OBD2 cable it made a connection but did not show any codes, said there were no diagnostic trouble codes. I know this is not correct because my buddy has a several thousand dollar snap-on scanner and he scanned it early that day and it showed an exhaust back pressure code. Can someone tell me what is the deal with the computers in our trucks. Do we have OBD1 or 2 computers? And does anyone have experience with my scanner?

[late_99_PSD]

Your truck is OBD2. Anything after 95' has an OBD2 connector on it. While it does have an OBD2 plug on it, it is not mandated by the federal government to comply to the OBD2 standards because it is a diesel. OBD2 was intended to be used for smog and emissions testing. Since it is a diesel it dosent need to follow these guidelines, therefore many scanners will not read OBD2 on diesels because they don't follow the federal rules. Better scanners, like your buddys snap-on are designed to read the diesels OBD2 codes. Most people on here use auto enginuity scanners, fairly cheep and are fairly easy to use. Hope this helps!