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Old 07-01-2009, 02:59 PM   #1
Scooby Specialist
Member#: 16197
Join Date: Mar 2002
Chapter/Region: South East
Location: Georgia
05 LGT 18G-beater
12' Coyote Stang M6

Default P1507 and Neutral Switch info thread....

I was throwing a P1507 code on my 2002 wrx and was searching for a solution on how to fix it. I got alot of non concrete info in a bunch of threads, especially on the neutral switch, where it is, and how to fix it.

First the P1507, Idle control system malfunction. If you are throwing this code you have exactly two places to look at, the IACV(idle air control valve) located on top of the throttle body mounted with two phillips head screws, or you have a faulty neutral switch(apparently pretty common, especially pre-wrx era cars). So, lets pretend your IACV is gummed and gunked up. Remember this is your idle air control valve which means there is a moving piece in there. So you most likely wont be able to just spray it with carb cleaner or soak it in rubbing alcohol to fix it(this is what i tried first). Its hard to describe what the actual moving valve piece looks like, just know there is a moving object in there that is spring loaded...if you push it in it should spring back quickly once released(you can push on it with a flat head screw driver, or anything thin). Mine was returning slowly, on top of that it wasnt returning all the way to its out position. So i filled my IACV up with rubbing alcohol and just kept actuating the valve with my flat head...it finally started to free up and spring quickly and easily back to its fully extended position. This took me 4-5 attempts of putting the IACV on and off the car and testing, and then cleaning some more. Luckily it takes roughly 15-20 secs to install and remove the IACV. *NOTE*-you will have to replace the IACV gasket, the rubber gasket expands after new and doesnt fit again once removing the IACV. I ordered mine from subarugenuieparts, just email them telling them you are looking for an IACV gasket and what model year your car is, they will get you what you need. I think it was like $7.

Next, if you have a faulty neutral switch. First, it is located on the driver side of the transmission towards the rear of the transmission. I found this link that shows it. http://www.surrealmirage.com/subaru/...location07.jpg
You need nothing more then a 3/4 or 19mm, i think, open ended wrench. Jack the car up, unscrew the switch, remove it from the harness(kinda a bitch until you realize how it releases). Plug in the new switch, screw it back into the trans. Again, i ordered mine from subarugenuineparts, it cost $27. Email them, tell them what you need and what year
This should apply most if not all subaru 5spds(NOT auto's, they are different and switches are more expensive), including older legacies and impreza's.

If you are searching and this thread helped, post up. If you have anything to add, lets hear it.
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Old 07-01-2009, 09:31 PM   #2
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Member#: 133012
Join Date: Nov 2006
Chapter/Region: MWSOC
Location: Kansas City
2015 STi
Lightning Red


I just wanted to add a note about the NSS. If you have a tactrix cable, you can step into the ECU either using Romraider logger or ecuExplorer and select the neutral position switch. The value should change from 0 to 1 (on to off) as you go into gears and back to neutral. If the values do not change, then your NSS is bad.

If you do not have a cable/logger, you can still manually test this if you have a multimeter. The wire runs into the ecu, and the pin location varies by year. Ecu pinout information can be found at http://www.northursalia.com/modifica...ng/wiring.html Again, you should be looking for a changing voltage (0v in one, 12v in the other) The relativity between ground and 12v varies between some years (some show 12v in gear, some show 12v in neutral) but the idea remains the same.

Also, a note on the IACV, to better clean the assembly, you can remove the stepper motor (which is magnetic btw) from the valve body assembly and clean the drive system that way. I posted in the IACV thread about this, where the bearing assembly can gum up over time as it is not sealed. Soaking it in gasoline or similar solvent and spinning the assembly and swabbing out any buildup can greatly relieve any issues with a sticking IACV.
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Old 11-26-2009, 05:44 AM   #3
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Member#: 220143
Join Date: Aug 2009

I'm having a hard time finding a solution to my problem.

I'm from Australia and have a 1998 WRX - EJ20G I believe?

I have the following CEL:

Code 24 - Idle Air Control Solenoid Valve:

Contents of diagnosis: Idle air control valve inoperative. (Abnormal signal produced in monitor circuit.)

Fail-safe Operation: Prevents abnormal engine speed using "fuel cut" in relation to engine speed, vehicle speed and throttle valve position.

The manual also states that there are 8 sensors that need to be working in order for the IAC to work.

These are:

Crankshaft Position Sensor (changed 3 months ago to a second hand one)
Camshaft Position Sensor
Throttle Position Sensor
Engine Coolant Temperature Sensor
Vehicle Speed Sensor 2 (changed to a brand new OEM Subaru one)
Ignition Switch
A/C Switch
Neutral Position Switch (MT) (changed to a brand new OEM Subaru one)

The problem is stated in the service manual, the ECU cuts fuel around 4500rpm.

The car fines fine, power is good until the ECU cuts fuel, the idle is perfect. I don't know what's going on?!

Can anyone please point me in the right direction?
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Old 06-06-2010, 04:07 PM   #4
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Chapter/Region: NESIC
2002 scooby
WRC blue


yea but if any of those 8 sensors were bad they throw a code hence they are electrical and tied to the ECU so if one of them was bad you would knw
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Old 07-17-2010, 02:53 PM   #5
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Join Date: Jun 2009
Chapter/Region: MAIC
Location: Lynchburg, VA
2003 WRX
Aspen White

Default grrrr

My car has just thrown the code p1507 and I can't figure out what's wrong.. I checked my nss and its reading propper voltage and I just cleaned my iacv...any help would be great...thanks.
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Old 05-02-2011, 03:29 PM   #6
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Join Date: Jan 2010
Chapter/Region: RMIC
Location: 5280'
2006 OBP WRX Wagon


Sorry to dig this up again but can someone tell me if the iavc gaskets are the same for gd turbo and n/a models?
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Old 06-18-2011, 11:13 AM   #7
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Default P1507 code fixed with neutral switch

Originally Posted by panheadwrx89 View Post
My car has just thrown the code p1507 and I can't figure out what's wrong.. I checked my nss and its reading propper voltage and I just cleaned my iacv...any help would be great...thanks.
I have a 5-speed 2002 Subaru Outback wagon with 150k on it. Periodically it'd stall when slowing down while downshifting. I would reliably get the CEL every time I'd downshift going downhill. My code reader showed P1507.

I replaced the neutral switch ($30) and that fixed the problem. The switch was pretty easy to install - basically unscrewing the old one from the transmission, disconnecting the electrical plug, then reverse with the new one. Once you're under the car it's a 20 minute job tops. Good luck.

LINK: http://www.porcupine73.com/endwrench...TroubSum04.pdf

Last edited by PCT; 06-22-2011 at 07:20 PM.
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Old 10-06-2011, 04:59 PM   #8
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Member#: 258843
Join Date: Sep 2010
1998 Impreza 2.5RS


Hi guys,
I tested my NSS and got:
Neutral: 4.75V
1st: 0V
2nd: 0V
3rd: 4.75V
4th: 0.03V
5th: 0V
R: 0V

Does that mean the switch is bad? I have the same P1507 code and cleaned the IAC already
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Old 02-20-2012, 08:00 PM   #9
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Join Date: Feb 2012

Does anyone know if on a 2002 legacy 5spd if the neutral switch is postive or negitive trigger?

Going by the schematics it seems negitive but by the ECU I/O testing sheet it should be positive? So that puts a little confusion into testing

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Old 05-05-2013, 12:58 PM   #10
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Member#: 355524
Join Date: May 2013
Location: Jacksonville, NC
2006 wrx


I'm throwing the. same code but my idle seems to be fine, but I'm also throwing a p1088 code. Can somebody help me out here?
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