[Soundy]

I was going to add an example to that post, and forgot: we recently installed a GPS fleet tracking system into some brand new Hino delivery trucks - they transmit the truck's location via 3G service. Followed the GPS manufacturer's instructions for wiring them in and placing them (they even had specific wiring instructions for these trucks, showing what wires to tie into).

In the first truck, because of differences in the under-dash layout, the receiver had to be mounted close to the vehicle's ECU... took a lot of phone troubleshooting with both the GPS manufacturer and Hino techs to figure out that the 3G signal was causing the trucks to intermittently not start properly, and relocating the receiver by a foot or so cleared it up.

So... yeah. This is why extensive testing and re-testing must be done to certify tech for use on a plane... and re-done for every different design of plane.