01 PF Code P0505 - IAC Valve

[Swanicyouth]

***Left my 01 idling outside the store for a few minutes last night. Come out SES light on. Scan it, code P0505 IAC valve. Re-set the light, started it a few more times, let it sit, restart - let it idle - light stays off. I did some research, and I found some people had this code and replaced the IAC valve to no avail. Also, apparently coolant runs through this valve, it can leak internally, short it out, and fry the ECM. Background: 4 days ago I took apart the air tubing and cleaned the throttle plates. Light never came one before or until 4 days after. If it comes on again, I will try the idle re-learn procedure. Car idles exetremely smooth, tach on dash reads about 800. No driveability issues at all. Anyone deal with this code? What did you do? Thanks !

[Towncivilian]

Perhaps cleaning the IACV would help - though I don't know how to go about this as I've never done it or even removed the IACV. Hopefully someone else knows more.

Are you sure coolant runs through this valve? It's an idle air control valve, so one would think it lets in air to bypass the closed throttle body at idle.

A new IACV is $244.25 - pretty expensive.

[Swanicyouth]

Yeah, Im pretty sure coolant runs through it. It has 2 vacuum like hoses going in and out of it. First, I thought they were vacuum hoses, but then I read they were coolant hoses and sometimes the valve can leak coolant internally and short it out. People have had their ECMs fried because of this. It seems like anyone who touches this valve has idle problems afterwards. Car idles perfectly, no issues. Just SES light came on once.

[Towncivilian]

Hmm... if it came on once, then you reset it and it disappeared I probably wouldn't worry about it.

[Swanicyouth]

Yeah I'm not really worried about the IAC Valve, mainly I'm worried about it shorting out and frying the ECM. I was just wondering if anyone here had that experience with the P0505 code. If you read the net, seems like everyone who has this code ended up with a fried ECM. But I'm sure 90 percent of the people with this code just fix it and don't post. I was hoping to pull some experience out of someone. If I get it again I'll replace the valve, just because I don't want it shorting out frying the ECM. Looking around, it looks like there are two main aftermarket companies that make this valve: Hitachi and Standard. The funny thing is, I've seen them online as high as $290 and as low as $160.33 - why would anyone order anything but the cheapest part (its a brand new Hitachi with free shipping). Just out of curiosity, I'm going to price it at my local Nissan dealer also. Started the truck again this morning, idle smooth at about 800 and no SES.
*** Update, no SES light on, but I stopped at the Nissan dealer to price out an IAC motor. They told me $315.00. But, then the guy said for $314.00 I can get the whole throttle body with the idle motor already built up on it. I believe both were Nissan parts, he printed me stuff from the Nissan parts diagram. Maybe the throttle body is a reman, but since it would be free, looks like that would be the way to go. The guy also said he rareley (if ever) sell these for 3.5L PFs and keeps none in stock. Also, he said he cant recall ever selling an ECM for a PF - so I guess it's not as common as a problem as the internet would have you believe.

[smancer]

I got that code when I had to unplug and remove the IACV when I changed my spark plugs. I did the idle relearning procedure and then reset the code but it still came on again after a few days. I tried disconnecting the battery for a long period and then reset the code again but the SES came back on. Since I wasn't experiencing any issues and I didn't want to spend a ton of $$$ to replace the IACV, I just drove with the SES light on for about a week and it just turned off by itself and everything is good now.

[Swanicyouth]

Ok, here is where I'm at with code P0505. Cleaned the throttle plates 3 days before SES came on. I've owned the car 2.5 months and it never came on before. Also, I never had or have any idle or driveability issues. Drove around all day yesterday after clearing the code - no light. Finally, last night I was letting the car idle turning off and on defogger and other things that can change the idle. Then all of a sudden light came on again. I'm going to make a more detailed check this weekend to make sure no air or vacuum leaks. But looking at it with a flashlight last night it all looked ok. To test the valve, you check it with an ohm meter, and it looks like you may have to take it off to get at the terminals on the valve accurately. If that's the case, and I have it off, I will put a new Hitachi valve on (160$ online - just for valve, Nissan want 315$ for valve or throttle body with valve and TPS sensor already bolted on). Again, I'm a little afraid of letting it go and coolant leaks into the valve, as the valve has coolant running through the base and this issue is not unheard of. I believe cleaning the throttle plates with with the throttle plate cleaner spray ruined the valve. It certainly got in it, as the valve sits almost directly at the bottom of the chamber. Also, I couldn't find anywhere in the Nissan service manual where they reccomend cleaning throttle plates by this or any other method. Any input is welcome.

[ARKQX33V6]

IAV allows air into and around throttle plate at idle since plate is shut, but a plugged IA valve with carbon or its operation is decreased bad voltage, the proper amount of air is not entering for idle combustion and bad idle is the result.

Time and patience and a little carb cleaner can remedy a plugged valve but a bad voltage consumer means a new valve.

While your in the cleaning mode check the EGR,it most likely is in need of carbon removal. Smack it gently, you may dislodge the carbon, failing that a dismantle is needed.

If the IA valve is plugged an engine de-coke may be needed

[smancer]

I forgot to mention before that I also cleaned my throttle body first before I removed the IACV to access the spark plug below it. I only got the code probably after 45min of driving the next day then everytime I reset the code the SES light would stay off for a while then come back on and I tried so many things from the service manual still got the code. Maybe some of the cleaner that went down didn't flash off yet or something.

If your not experiencing any idle issues maybe try what I did and wait it out for a bit maybe it will turn off by itself like mine. But then again I'm not an expert it's just a suggestion. I just thought if the IACV was malfunctioning I would notice a difference but it was running all normal so I took the risk and ignored the SES light for a bit.

[Swanicyouth]

This was the kind of info I was looking for. IIt sounds like cleaning throttle plates somehow may cause an SES, as we have almost identicle experiences. Either it takes a while for the vehicle to relearn the idle again correctly or the spray is messing up the valve. You mentioned it went away. How long since your SES light been off( how long since you have had a problem?) Thanks!

[Towncivilian]

I thoroughly cleaned my throttle body since it was disconnected from the manifold and haven't had any issues. I didn't touch the IACV, though. I used CRC throttle body cleaner and a rag.

I also cleaned the front of the plate once early this year without removing the throttle body, no problem there either. I used the same cleaner.

[smancer]

This was the kind of info I was looking for. IIt sounds like cleaning throttle plates somehow may cause an SES, as we have almost identicle experiences. Either it takes a while for the vehicle to relearn the idle again correctly or the spray is messing up the valve. You mentioned it went away. How long since your SES light been off( how long since you have had a problem?) Thanks!

MY SES light has been off for probably 6 months now. So far so good everything is running great.

[Swanicyouth]

Where I'm at with this. I pulled the ECM the other day to check there is no sign of anything being burnt. All looked and smelled well. Apparently, this issue with the P0505 code and shorted IAC Valves causing burnt ECMs is more common on 3L Maximas with electronic motor mounts. I saw a few posts about this happening on a PF, but I dont think that's what I have. As most that say they have experienced this say there ECM looked or smelled burnt. Also, my idle is smooth and steady(even with the SES on); and many/all with burnt ECMs say their idle was way off and or hunting up and down. I was able to re- set the idle so it idles at 750 in gear and about 850 in neutral. It seems every so often if the vehicle is left to idle in park or neutral the idle no longer stays at 850, but settles at 950. If left to idle at that rpm its sets a SES. All this was done first or second trip after re-learning the idle, because I kept checking where it was at. The system seems very sensitive about that. If I drive it normally and don't let it sit in P or N, the light stays off. Before going further with this, I decided to order a new IAC Valve and throttle body gasket to install it. I decided that to conduct the tests accurately in the FSM, it's a lot easier to check the resistance values of the IAC Valve and TPS settings with the throttle body off. Since I'm taking it off to do this anyway, and there is a known problem with these valves shorting out and causing a major problem - I decided just to replace the valve if the light come on again - that is if the idle won't stick after a few days of not letting it idle for a few minutes in park or neutral. I've already checked for vacuum leaks with carb spray and visually inspected the harness and all looks good. The one thing is, the light will only come on if I let the truck idle for a while in Park or Neutral soon after performing an idle re-learn. Then, the idle settles slightly high. But if I drive it normally and don't let it idle In park or neutral the light stays out. I'm wondering if it takes a while for the idle re-learn to permanently set - a few days maybe of not letting it idle a few minutes in park or neutral to check it. As what I mean is, I keep checking it by allowing prolonged idle times in park after I re-learned the idle. I haven't done this in the past two days and all seems fine. MAybe the idle takes a while to stick after the re-learn and prolonged park or neutral idling was throwing it off. Idling at 750 in Drive seems not to cause a problem and that's where it stays at if not left to idle in park or neutral a while. I will see. The new valve is coming in a few days. I'll keep driving it. If the SES light stays off, I'm not going to mess with it. I'll let it idle a bit in park or neutral in a few days and see what happens.

[Swanicyouth]

Well, here is where I am at with this. Still need help. Replaced IAC VALVE, reset idle, did idle air volume learning and still the same. P0505 if I let it idle in park a few times. But, idle is solid at about 800. So, it wasn't the valve. As long as I put it in Drive right after starting all is fine, but put it in park, idle goes up to 900 and it triggers the code. Also, the idle jumps slightly when backing off the throttle when driving. Also, I adjusted the throttle position switch when I had the throttle body out. Same. This all started after cleaning the throttle plates (see above). My next guess is a MAF sensor. They are cheap on EBay. Can anyone help?

[smancer]

Hmmm that's odd something else is triggering the error for sure. That sucks that replacing the IACV itself didn't resolve the problem. I thought it was my MAF also when my pathy threw the SES so I pulled my MAF and cleaned it but didn't help with the code. I guess it's worth a shot and it's cheap maintenance too. Other than that I don't know any other things you can try. You could bring it to the dealer but i'm sure it will cost you an arm and a leg for them to diagnose it.

[Swanicyouth]

I think where I'm at now is Im going to either wait for the problem to get worse or have Circuit Board Medics look at my ECM. The P0505 code means there is a short in the IAC valve circuit. I replaced the valve, check the wiring and old valve - both where ok. I'm thinking I sprayed to much cleaner in the throttle plates and it stayed wet - and, when I started it the ECM was damaged. Ive never heard of this before, but I'm not sure where to go next.

[QX4Cameo]

I think where I'm at now is Im going to either wait for the problem to get worse or have Circuit Board Medics look at my ECM. The P0505 code means there is a short in the IAC valve circuit. I replaced the valve, check the wiring and old valve - both where ok. I'm thinking I sprayed to much cleaner in the throttle plates and it stayed wet - and, when I started it the ECM was damaged. Ive never heard of this before, but I'm not sure where to go next.

have you found an outcome the the problem? i am experiencing similar issues as well with my 2001 qx4