Testing your guino build
 

FYI, I took some readings off a working MPGuino and posted the results on the wiki:
Mpguino tests - EcoModder

Looks good. Personally, I went the route if getting a preassembled Arduino Diecimila. It seems to work fine so far. I think it's a little larger, but it cut down on the amount of soldering.

Yup, pre-assembled can benefit from the same tests since you still need to add some interface circuitry. The iduino especially since you have to make your own 7805 power supply for it. A lot of noise is made about damaging this or that, so these tests make a nice sanity check that you haven't built a direct short at least.

Great post, I think I will put a link to the wiki in the iDuino MPGuino page. The more problems I see people having, the more I would have liked to be able to test these kinds of things before hooking up in the car. Thanks dcb!