CEL p0850, p0507, Still chasing these demons. Getting Desperate.

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P17ch_8l4ck

Member
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2003 Mazdaspeed Protege
After changing the clutch peddle position switch, my car threw the codes for Neutral/Park Safety Switch Circuit Fault (P0850), and Idle RPMS Higher than expected (P0507). The car was having some bubble idle, and when I'm stopped if I let out the clutch and have the brakes pressed down, the RPMs will rise to about 1300, and at times rise up to 1500 RPMs, drop back down to 1000, then rise and then drop, etc. I had also noticed that when I brake from higher acceleration the RPMs drop to near stall, though never stall, then rise back up to idle.

I did my research on here and read that it was just the neutral safety switch and to just change it out, the switch being the one nearest the fire wall. I did that and have not had any change to my codes even after clearing them. After fiddling with different theories I exhausted all my knowledge and my patience and took it to my mechanic. After waiting 6 hours while he worked on it, he was not able to get the codes to go away. This really threw him for a loop. Thankfully he only charged me 1 hour of labor.

I would really appreciate any help. I'm in desperate need of an inspection and here in Texas you can't pass inspection with a CEL. Anyone who can figure this out would be my ultimate hero.

If there is some information that I haven't provided please ask and I will do my best to clarify.
 
lol nice i was born in austin that sucks though have you adjusted the idle screw? and have you ever changed the wastegate that might be why your idle is dipping down
 
nah, the neutral safety switch would cause the high idle. so i see you changed the switch, you sure you got the right part? that could be one of the dummy switches, i think its a dummy speedo since P5's and other proteges without ABS use that, but since we have ABS speedo runs off of that.
 
Sorry for the late reply. Been outta town for family events.

This is the part that I put in:
AIRTEX / WELLS Part # 1S5739

This is the same part as the reverse light switch.

I don't quite understand what you mean by dummy switch. Would you mind expanding on that?
 
If you did replace that neutral safety switch, did the problem with idle go away with the code being thrown? If so, the car needs to be turned on and off around 10 times before the code is cycled out of the ECU.
 
Actually I have done both. The first time I did it, I replaced the wrong one then I ordered another one and replaced the correct one. And neither the code for the switch or the idle problem have gone away.
 
i couldnt get the trouble tree but it says from top to bottom

possible causes
accelator cable misadjusted
cruise controller cable misadjusted
idle air control valve malfunction
PCM malfunction
throttle valve malfunction
vaccum hose disconnected

id say just check what u can get to man i wish i could copy the trouble tree for p0507 for u but its not letting me lol
 
and usually the lowest number dtc causes the higher one so take care of the lower number and the higher one might go away.
 
Okay, so I traced the neutral switch back and found where one of the wires in the harness had been cut, probably when I had the engine replaced. I sliced those together and the idling problem has gone away, but I'm still getting the switch CEL code. Aside from some bubble idle issues, it would appear that the symptoms have gone away, other than the code.
 
Glad to hear you fixed it. Last night i saw a spicy on south 1st street was that you? It i didnt have my girlfriend with me i would have turned in to the store it was parked at.
 
Nice, another Austinite on here. Me and some buddies are thinking of taking on the twisted sisters, or whatever they are called, soon. They are BMW guys, 335i's. I normally take point so they don't get too excited and loose me hehe.
 
My dad and I are going out to Texas World Speedway in College Station for an on track event at the end of march, can't wait to see what the MSP can do almost stock with about 100k miles.
 
Im having the same issue with the idle when i push my clutch in it will drop and when i push my brake in sometimes it will raise the rpms to 1500 to 2000, in which i have been working on this for the past week and checked for vaccum leaks and poor connections in different terminals in which i have found a plug that is not connected and think that it is the neutral safety switch but i can not guarentte due to not having a well enough diagram, pictures, video, or any help from mechanics in reguards to this. I have rebuilt my transmission and have had a new clutch put in by a mechanic around 6 months ago in which the problem could of occurred but i wouldnt of known for sure due to my check engine bulb going out on me and i have recentley replaced and is continueously coming back with every step im taking to fix this problem due to not passing Missouri emissions. If there is any help with the location of this neutral safety switch or why i might have an extra cord that is not plugged in it would be greatly appreciated. I do see on the top of my transmission on the driver side a connection that is a high tower but has a hollow inside that looks like it is a dummy terminal that the plug fits in but it doesnt assist with the problem and im still not exactly sure where this neutral safety switch is, ahhhhhh!!!!!!!!! HELP ME PLEASE . . . ps im throwing two codes the P0850 (neutral safety switch) and P0507 (Idle control system RPM higher than usual) but my car runs GREAT other then that . . . emissions are stopping me from driving my ride, so so so sad
 
While I can't guarantee it will fix your pproblem, I too had a high idle with the code P0850. The dummy plug you have is actually because the MSP doesnt have a speedo sensor in the transmission, therefore theres no reason to have a plug. Getting a new neutral safety switch cured my problem and its found at the bottom and back of the transmission. Look at this pdf to take a look:
http://www.mazdaspd.com/resources/Transmission_Rebuild.pdf
 
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