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Disconnect transmission sensors?

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I've  had a recurring problem on my '99, ever since I bought the car, where every other race weekend (or so), the car will throw code P0705 ("Neutral Switch Circuit Malfunction").   It happens so frequently that I've gotten to almost ignoring the CEL.


Some years back I disconnected one (or both?) sensors and the codes disappeared - I never noticed any impact on engine performance.


Last time we had the engine out of the car, they got reconnected and I'm throwing the codes again.  I'd like to disconnect it again, but I can't remember which sensor wires I disconnected/snipped last time.   The one on the top of the transmission housing (the one that is almost impossible to get a wrench on from under the car), or the one on the side of the housing?  (or both?)

Any words of advice or warning about doing this?









Steve Tynor

'99 SM

Atlanta, GA


Bona fide - A bonafide Spec Miata driver

Jeff Wasilko

Jeff Wasilko


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  • Location:Boston, MA
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One of the switches is reverse, one is neutral, and on the passenger side rear is the speed sensor.

To verify you should be able to disconnect one and see if you still have backup lights...



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The one on top of the transmission is the neutral switch. One on the drivers side is the reverse switch. 


Reverse switch just activates the back up lights, from what I recall. that one should have two bullet type connectors and polarity doesn't matter, ie: you can connect either wire. I race mine so I don't even have them connected! 


The neutral switch should have snap in connectors, and I'm pretty sure it's the same thing, polarity doesn't matter. BUT, this switch is a little more important in that it tells the engine you're in neutral, so the ECU can tell the engine what to do (idle speed, etc). 

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