I have a 2001 Protege with a manual transmission. There was a leak from the transmission and after an inspection the dealer told me it was from the speed sensor. After his quote of nearly $300 to replace it I decided to have a look. I located the speed sensor on the top of the transfer case. It is hard plastic and has couple wires running into the top. The dealer said a new one would be about $30.

It is held on by only one 10mm bolt and was not too difficult to get off. Once I removed it I saw where the 'O' ring needed replacement but to my surprise it appears that the speed sensor doesn't do anything other than plug a hole and serve as a place for the wiring bundle to plug in to.. The wires don't connect to anything and there is nothing that goes down into the transmission. I have seen some pictures of older ones that look similiar to this one but have a gear assembly on the end.

So my question is what is the purpose of this dummy sensor? It appears there is no earthly reason to have it other than to plug a hole that maybe wasn't needed anymore and they didn't want to re-manufacture the transmission housing. If that's true then why have wires running to it? And I won't even address the issue of why they want to charge $30 for a piece of plastic that doesn't do anything - and of course the 'O' ring isn't sold separately even though that is my plan.

Thanks