Helen, you haven't cleared up if it's stick or pedal switched?

I'd forget the error code first of all. Fault 06 is what your creating by pressing down on your accelerator pedal while the truck is in neutral, I can't see it being the accelerator pot as you say you've only lost drive in one direction - correct?

You say your "switches" don't look burnt? Are you talking about your contactors here or are you referring to your directional selection switches? How can you say your switches don't look burnt? They are tiny encased micro switches, you'd never see burning on them unless you smashed them apart somehow.

It's a safe bet what Kev's getting at is right, check your reverse micro switch - not the reverse contactor tips which I think is what your looking at?