Hmm, could be, but the system has 'dual redundancy', i.e. two independent position sensors on the pedal and butterfly, so both would have to be faulty. Could be the motor or harness though. I don't know why they can't just hook up a standard OBDII logger. Even if there aren't any codes being thrown you should be able to get some clues from the logged data traces (revs, ignition, speed, fuelling, throttle position etc.) what is happening.

Good Luck Sharon, hope you get a solution soon!