isolating neutral signal

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Forum Name: General Discussion
Forum Discription: General Mobile Electronics Questions and Answers
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=107891
Printed Date: May 11, 2024 at 3:36 AM

Topic: isolating neutral signal

Posted By: chiarlanza
Subject: isolating neutral signal
Date Posted: October 02, 2008 at 9:33 PM

Help..

I have an 08 Nissan w/ a manual trans. On the trans is a neutral position sensor. The sensor has 2 wires going ot the BCM (I believe). I think it's a MUX, or some sort of signal other then a simple (-) ground signal.

I would like to use this switch w/ my remote starter to tell it when the truck is in neutral.

How can I isolate ths signal to throw a ground signal to the remote starter when it's in neutral, and still not effect the signal going to the BCM. Diodes??

Replies:

Posted By: i am an idiot
Date Posted: October 03, 2008 at 5:18 AM

If you can verify that the switch simply connects the 2 wires together when the vehicle is in neutral. You could then use the switch to trigger 2 relays, one for ground to the alarm. The other relay would be connected to the factory wiring to duplicate what the switch is doing.

Posted By: KPierson
Date Posted: October 03, 2008 at 12:50 PM

What kind of Nissan do you have? All the Nissans I have seen have a simple (-) signal coming from the P/NP switch mounted inside the tranny to the ECU. I have access to most of the Nissan service manuals, so if you tell me what kind of Nissan you have I may be able to look it up.

If you do need to use relays make sure you use a relay with an extremely small amount of current draw, as a standard automotive relay will kill your battery in a short amount of time.

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Kevin Pierson

Posted By: chiarlanza
Date Posted: October 03, 2008 at 1:00 PM

It's a 2008 Nissan Xterra (X). It has the 6 speed manual in it.. Any help w/ the FSM would be great I have been looking for the factory manual w/o such luck..

Posted By: KPierson
Date Posted: October 03, 2008 at 4:03 PM

I don't have access to the '08 manual yet, but the '07s P/NP switch is connected to pin 102 of the ECU (NOT BCM, completely different box). The color is orange and it is at ground when the tranny is in N and 12vdc when the tranny is in any gear.

There are two wires on the switch, one goes to ground the other goes to the ECU. The 12vdc voltage is most likely the result of a pull up resistor inside the ECU (ie don't try to power a relay off of it).

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Kevin Pierson

Posted By: KPierson
Date Posted: October 03, 2008 at 4:06 PM

And I guess to answer your original question you can use diodes to isolate it if you feel it is necesarry. I wouldn't use a diode, I would just hook it up. The ECU doesn't use this sensor for anything overly useful anyway (no load rev protection).

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Kevin Pierson

Posted By: chiarlanza
Date Posted: October 04, 2008 at 6:28 PM

Thanks for all of the help.. I am going to put a 561 into the truck over the weekend.. I will let you know how i make out.. I am not going to bother to dioade it. I am gonna run it right off the wire..

Thanks again..