looking at the ur pic, i can say any polarity can work and u can use a small board with a good quality 5volt regulator to test the switch.
so ESP is running on ur car! Thats freakin amazing man.
And even if its not geting the car going on factory ecu with out the esp cuttiing ur throttle is amazing tooo.
Gr8 respect man.

__________________
Jay,
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-1995 Blue W202 C36 AMG (M) SOLD ;(
-1995 Black W140 S500 (Lady)
-1992 Black W124 E300 (Dima) (Ex-Mosselman
Twin turbo Kit).
-1988 Black W124 300 E 4-Matic.(Nadeen)
-1983 Brown W126 500SEL.(Old Lady)(Sold)
-1981 Gold W123 280CE.(Dareen)(Sold)
http://www.youtube.com/user/jayrasheed