Tying Neutral Safety Wire into Hood Pin Q
Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=36209
Printed Date: May 16, 2025 at 11:55 AM
Topic: Tying Neutral Safety Wire into Hood Pin Q
Posted By: B94Sport
Subject: Tying Neutral Safety Wire into Hood Pin Q
Date Posted: July 26, 2004 at 2:49 PM
I would like to tie the neutral safety wire off of my ECU into my hood pin shutdown switch on my alarm, so that the remote start will not activate unless the car is in neutral. This is on a 6 speed transmission (Subaru WRX STi) that already has a neutral position sensor built in. I have heard that the neutral safety wire should be tied into the hood pin shutdown using a diode, but I don't see how it can work... The hood pin currently shows 12 volts when the hood is closed, and ground when it is opened (magnetic hood pin). The neutral safety wire shows 12 volts when the vehicle is in neutral, and ground when in gear. If I want to wire both of these to the hood pin input on the alarm, how can I make it so that everything still works correctly? It seems to me that if the hood was open but the the car was still in neutral, it would be possible to remote start it because the hood pin input on the brain would still see 12 volts from the neutral safety wire. Likewise it would still be possible to remote start the car if the hood was closed but the transmission was not in neutral, because the hood pin input on the brain would see 12 volts from the hood pin. How can I use diodes to isolate these two inputs from one another, and make it so that if one of the inputs is throwing a ground, the brain input sees ground?
Replies:
Posted By: draasch
Date Posted: July 26, 2004 at 5:44 PM
what unit are you using????? most units have a SNS wire....and a hood pin switch wire.... ------------- Good Luck
David
Ace Security
813-376-9778
Tampa
Donate to the 12volt
Posted By: B94Sport
Date Posted: July 26, 2004 at 6:16 PM
Oh, I am using a Compustar 2WSS-AS with the CM3000 brain. It only has a hood pin input, no NS wire input.
Posted By: B94Sport
Date Posted: July 27, 2004 at 5:55 AM
bump
Posted By: profuse007
Date Posted: July 27, 2004 at 7:57 AM
-im assuming you let the brain to function on automatic tranny since you have NSS.
-so tie the hood and NSS w/ a diode facing the hood pin and another one facing the NSS computer module.
-whats the exact model of this Subaru?
-whats the wire for the NSS and its location?
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Houston,TX
"The two most common elements in the universe are H+ and stupidity" (Ellison).
Posted By: B94Sport
Date Posted: July 27, 2004 at 9:27 AM
Exact model: 2005 Subaru Impreza WRX STi NSS wire and location: Pin 9 on B137 connector at the ECU. Don't remember the exact colors, but I have it marked off.
Posted By: profuse007
Date Posted: July 27, 2004 at 10:45 AM
thanks
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Houston,TX
"The two most common elements in the universe are H+ and stupidity" (Ellison).
Posted By: JWorm
Date Posted: July 27, 2004 at 9:00 PM
B94Sport wrote:
It seems to me that if the hood was open but the the car was still in neutral, it would be possible to remote start it because the hood pin input on the brain would still see 12 volts from the neutral safety wire. Likewise it would still be possible to remote start the car if the hood was closed but the transmission was not in neutral, because the hood pin input on the brain would see 12 volts from the hood pin. How can I use diodes to isolate these two inputs from one another, and make it so that if one of the inputs is throwing a ground, the brain input sees ground?
The 2 diodes you install prevent the +12v from ever going to the alarm brain. Only the ground from the hoodpin, the ground from the NPS (Neutral Position Sensor) or both goes thru to the brain. I suggest clicking the link on the top left of this page that says "diodes" and doing a little reading.
If anyone wants more info on Neutral Position wires for Subaru, I could probably help you out with location/color of wires. I have info on most Subaru's from the last 5 years or so.
Posted By: B94Sport
Date Posted: July 27, 2004 at 9:27 PM
JWorm] wrote:
he 2 diodes you install prevent the +12v from ever going to the alarm brain. Only the ground from the hoodpin, the ground from the NPS (Neutral Position Sensor) or both goes thru to the brain. I suggest clicking the link on the top left of this page that says "diodes" and doing a little reading.
If anyone wants more info on Neutral Position wires for Subaru, I could probably help you out with location/color of wires. I have info on most Subaru's from the last 5 years or so.
I read that Diodes link, and still don't see how this can work... If only grounds go through to the brain, how will the brain get the +12 volt signal when the hood is shut, the car is in neutral, and thus should start?
Posted By: JWorm
Date Posted: July 27, 2004 at 11:21 PM
The brain doesn't need to see +12v in order for it to remote start. It just needs to NOT see a good ground.
Posted By: B94Sport
Date Posted: July 28, 2004 at 5:01 AM
JWorm] wrote:
he brain doesn't need to see +12v in order for it to remote start. It just needs to NOT see a good ground.
I see... Now that I think about it, I remember that before I had my hood pin hooked up, the car would still start. Thanks for clearing that up for me! I will try it out and post the outcome.
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