Bobby J. Hughes wrote:

This question will show my lack on knowledge regarding the sensor and
trigger wheel. Could a extra sensor be located in a different position
and still work properly? Does the sensor just count teeth to determine
where it is or does it rely on a relationship between the factory
mounting position and the missing teeth?
 
Bobby
  

The correct answer is "C" (not "Si", although that would be correct, too).
Two things the computer has to "know" about those pulses: [1] which one
is #1, and [2] how many to expect before seeing #1 again.  Beyond that,
thaere has to be some kind of standard for how long after a pulse before
it should actually do something.

Traditionally, the first item was determined by having the #1 "pulse"
actually be two, or more, in quick succession - such as three notches
in the wheel with old enough space in between to insure that the state of
the pickup would change.  An alternative scheme is to have an extra-wide
"tooth" where the computer notices the lack of state change.  The more
teeth, aperatures, slots, etc., the easier it is to measure a change in
rotational speed. (time between pulses). 

You could put another sensor elsewhere, but you would have to
build into the detection circuit a way of allowing for the distance from
the original sensor.

Or you could add another reluctor and match or offset its timing to
get the same signal timing as the original.

Dale R.