David,
With regard to OBDII codes/protocols, there is a definite difference between GM/Ford products and all others (Chrysler following the European and Asian standards). The best/quickest explanation is here:
On-board diagnostics - Wikipedia, the free encyclopedia . This article gives the actual pin differences in the various standards. Then you have to add in the fact that the coding scheme allows for both generic/universal and manufacturer specific codes. So, it takes a fair amount of sophistication in the "reader" device to sort all this out. The unit I purchased seems to handle all this quite well (at least on the vehicles I mentioned).
While I have no personal experience with ScanGaugeII, I would suspect that it is probably not rigged to take all these different issues into consideration. At this point it would probably take a call to their customer service to find out what specific vehicles this unit works with.
Hope this helps,
Bob
