At 06:54 PM 6/21/2012, neil n wrote:
>Sorry. Wiring in an LED is a bad idea.
>
>Shunting an LED directly into TVS circuit would cause the supplied 5 volts
>to be sent back to ECU all the time; it would take the TVS out of the
>equation.

TVS?  Anyway, a) a worn throttle body may very well have to be
adjusted with the engine running; and b) a yellow LED and dropping
resistor in parallel with the throttle switch is an entirely
practical way to monitor the switch.  In practice you can run a
single wire from the hot side of the switch and take your ground from up front.

You were a bit confused about what the ECU is doing.  The ground side
of the switch is grounded.  The high side is supplied with five volts
limited at some smallish current and the ECU watches the voltage on
that pin.  High = open, low = closed.  It's threshold is set such
that you can steal some for an LED without changing its operation.

Yrs,
David