The four pole one is the one that tells the CIS-E system the Engine Temp, to fire the Cold Start Valve and Actuate the Idle Air Control Valve as well as the EHA adjustments depending on engine temp. It is called the Water Temp Sensor.

__________________
~Jamie
_________________
2003 Pewter C230K SC C1, C4, C5, C7, heated seats, CD Changer, and 6 Speed. ContiExtremes on the C7's.

1986 190E 2.3 Black, Auto, Mods to come soon.....