'85 WX What is the sensor at the back of the head? It has two tabs. The connector plug has one wire going to one contact and two wires going to the other. Etka is confusing. (possible understatement) "early" p/n is 056 919 369P "later" p/n is 171 919 521F but it is stated to be 1 pin. Does the "thermoneumatic valve" on the side of the block fail often? Thanks, Ed