AJ, here are two possibilities:

1. If you are using a Sears-type meter (set on freq/duty cycle) be sure to
press the upper left button to go from the "frequency" mode to the "duty-
cycle" mode. If you don't do this, you will be reading the "frequency" of
the signal, not the duty cycle. (I know, I did this).
a. Switch on freq/duty cycle
b. push upper left button to display DC.
c. red wire in hole #2, black wire in hole #3 (backwards from expected).

2. The engine manual says if you are seeing a constant 10% DC, you could have:
a. Bad sensor air volume meter connection. (don't know much about this
one, probably a reostat that could be checked like a throttle position
switch?)
b. Throttle valve switch not contacting, or defective.
(the throttle valve switch is on the linkage, should click when the
throttle is cracked open. Also, pull the wire and see if it changes
continuity when it clicks).

DG