Pretty sure it needs a signal... Worse, if you turn the unit on and it
doesn't get ignition after three starts it disables itself and can only
be reset with a diagnostic computer! I looked at the schematics once
and brought myself to believe that shorting two leads should clear an
error off the stack but haven't needed to test it yet. I've been
really disappointed with mine and with the service/installation that
I've gotten from the dealers down here in Australia and New Zealand.
YMMV, of course.

-- Tom.