Unable to diagnose 2001 LE/Dangerous as h**l [SOLVED - IACV issues]

[tee2]

Greetings,
I would like to start from the beginning, so that I can try to fully explain what is happening, and what I have tried to solve the problems.
I purchased a 2001 Nissan Pathfinder, last Friday, from a private seller. The guy lived about 2 miles from the Nissan dealership, so before I cut him a check, I drove the vehicle over there, and had a used vehicle inspection performed. Nothing came back, on their scanners. and the only real negative comments were that the A/C needs to be recharged, and that there was a hole in the left tire.
So, feeling confident, I drove the car back to the sellers house, and made the purchase. As a side note, this thing looks brand new. Not a single dent, or scratched interior. Moving on.
1-The next day, I was pulling out of the drive way, and heard what sounded like a quick, loud vibrating sound, from the front of the Pathfinder. I did not have any problems for the rest of the day.
2-Day two, I was driving around, and had to come to quick/sudden stop, from about 20mph. The car came to a complete stop just fine, but as soon as it did, the engine also shut off. I was able to turn the key, and it started up just fine.
3-The following day, I was backing out of my space, at the Home Depot parking lot, and as soon as I switched over to drive, the car started bucking back and fourth, kind of accelerating, then slowing down on it's own. When I would apply the brakes, they did not work....at all. I had to dodge a few abandoned carts, but luckily was able to avoid hitting anything. After a few seconds, the car started performing just fine. My first thought, was that the transmission was starting to crap out on me. I left the parking lot, and drove it over to a shop that specializes in transmission work. The guy got in there with his machines, and not a single error code was coming back. He told me that the transmission actually in great health. He even test drove it, for thirty minutes and didn't notice a single thing out of place.
At this point, I drove it down the street a few miles, and brought it to a different mechanic. He was trying to ind out what the problem was, test drove it, ran his tests, tested the engine, couldn't find a single thing wrong. He then told me it may be my ABS system, or a dirty throttle body. After giving him the green light, he cleaned my throttle body, and checked my ABS. ABS was working fine, with no issues. After replacing the air filter for good measure, I hoped for the best, and left. Car ran smooth, all the way to the car wash. After leaving the car wash, I didn't want to streak my windows, so I turned on the AC. Two blocks later, the damn thing started bucking all over again, and refused to come to a stop at a red light. After a very close encounter with a truck, I managed to pull over, turn off the AC, and the car, and called the NIssan dealership service center. I explained the problems that I was having, and told them everything that I have had checked, and the wonderful reply that I got, was pretty much, ''you checked everything we would check, don't know what to tell ya.''
Being frustrated as hell, I turned the car back on, and was able to take off. As I was driving I realized that I had not turned the AC back on. On the car ride back home, I really thought about what had been going on, and I realized that every single time the car was bucking, or refused to stop, or would shut off by itself, the AC was on. HOWEVER, the car still makes that loud vibrating noise, from time to time, after being put in reverse, then being put in drive.
The ride home was fine, and I thought that I had at least found the culprit, being the AC, but then later on that night, I pulled out of the drive way, (The AC had been off, since the car wash incident) and when I put the car into drive, another car was coming down the road, so I had to apply my brakes, before the other guy passed me. The was working fine, but then as soon I saw that guy coming, and applied the brakes, it was as if I had my foot on the gas, and the bakes at the same time. I had my foot on the brakes and thats it, but this thing was still revvin up. The Pathfinder had some Dr. Jekyll and Mr. Hyde to it. Part of it wanted to take off like a bat out of hell, ad the other side, wanted to stay put. I made a U-turn put that cursed beast back in the driveway and haven't gotten in it since.
I know I typed a lot, I'm just hoping someone could help me make some sense of this jacked up situation. Every car that I've had in the past, that would either have the same issues, or similar issues, I knew what was going on. But this thing, I just don't get it. To make it even worse, my mechanics, and the dealership, don't get it either.

>Vibration noises, while switching gears, but two independent mechanics and the NIssan service center, ran their tests with no errors.(only when first turning the car on, and if I back up, the put the car in drive)

Probems:

>Car has turned off, after slamming on the brakes, from 20mph.

.>When the AC is on, the car starts bucking down the road, and the brakes completely fail.

>Sometimes, while applying the brakes, and the brakes only, the car will stop, but as soon as it does, that engine will start to rev at a high rate. You have a feeling that this thing is about to take off on you. (even with the AC off)

>While backing up, and changing gears, there is a quick vibration noise/jolt from the front, but only after the car is started for the first time. If I were driving around, then put the car in reverse, then back in drive, the noise isn't there. IF I get in, turn it on, THEN back up>put in drive, that noise will be present.

Things I have tried:
>Had the dealership run a used car inspection, including engine, and transmission test. No errors.
>Had it inspected by a transmission specialty shop. No errors.
>Had a private mechanic test the engine, ABS, clean the throttle body, and replace the air filter.
> From what I understand, it's not my
-Throttle body
-Idle control valve
-spark plugs
-transmisson
'-engine
-ABS system.
Besides that, this thing looks brand new. Unfortunately, at this point, it's a giant a** beautiful paper weight.

[Buzzman]

I can't say for sure what the problem is either.
Ok, now having put in that disclaimer, first thing I would do, regardless of whether you get any codes or not, is to replace the IACV (Idle air control valve).
The fact that the engine stalled, and then revs up for no reason, points to that valve.
It is a known problem that these things (IACV) are failing on the 2001-2004 R50's.
If it fails, and you do not replace it right away, it will take out your ECM (computer).
It has been suggested on here by more than one poster that you should replace the valve as a matter of preventative maintenance. I would agree with that.
Be assured: it will fail at some point.
There are many good threads on this subject, so try a search.
Speaking from personal experience (I hesitated to replace mine, and it cost me money and time), I would strongly suggest you bite the bullet and replace it.
This is one of those instances where you replace the part first, and troubleshoot after (it goes against the grain, I know).
Keep us posted.

[barnaclebob]

Are you absolutely certain you are only pushing the brakes? The brakes should be able to overpower the engine.

[1998Baja]

as far as the transmission goes or the noise you hear, could it be coming from all those heat shields they put on the exhaust pipes? I know mine makes a rattling noise when i take off. Also, are there any service records on when the last time or if any time the transmission fluid has been changed?

[atraudes]

The most worrying part of all of this is the brakes not working. Like barnaclebob said, the brakes should be able to overpower the engine. You could be on the freeway, floor the gas, and still be able to come to a stop. Granted it won't be nearly as easy but it's absolutely possible. The only possible thing I can come up with is the ABS system going haywire somehow. Is the pedal immediately sinking to the floor, or is there pressure and you can't push it hard enough to stop, or is it something else?

In addition to replacing the IACV, replace the TPS (throttle position sensor). You can get some really bizarre symptoms when it heads south and they're known to go bad as well, albeit not as frequently. Make sure you calibrate it per the FSM when you do.

I would also pull the CEM/ECU/main computer and open it up. Make sure you don't have any corrosion, burnt components, etc. It's a bit of a pain to get to, but it's not so bad when you get the hang of how the bracket works. I don't think these cars have a separate ABS computer. If someone can confirm there is, pull and open that too.

I also wonder if any vacuum hoses are mixed up, causing some of the weirdness. Check the FSM and go over all vacuum hoses and make sure everything's lined up.

[04pathse]

It is a known problem that these things (IACV) are failing on the 2001-2004 R50's.

I don't think the 03 and 04 models have the same design IACV and they are not susceptible to the same problem as the earlier models, am I correct?

[atraudes]

How old is your brake fluid?

Based on this Car Talk discussion, there may be a correlation between the A/C, brakes, and IACV.

https://pilotonline.com/news/can-the-ac ... 815c4.html

[Buzzman]

It is a known problem that these things (IACV) are failing on the 2001-2004 R50's.

I don't think the 03 and 04 models have the same design IACV and they are not susceptible to the same problem as the earlier models, am I correct?

You could be right. I made an assumption that it affected all R50's with the 3.5 engine.
Now that I think of it, every thread regarding a failed IACV has been on the 2001 or 2002 model year.
Good call.

[atraudes]

I believe the 03 and 04 used drive-by-wire whereas the 01 and 02 used old school throttle cables. I'm guessing the drive-by-wire system doesn't need a separate IACV because it'll just crack it open as needed.

[Blindaviator]

What I see happening with the brakes is this... When the engine starts bucking and trying to die the vacuum in the engine drops... The brakes use vacuum to boost the braking power and when you lose it the brakes will still work but will be VERY hard to engage...

I wouldn't worry as much about the brakes until you solve the idle issue...

[atraudes]

Very true, and I'm guessing you're right. If the pedal is going to the floor with no resistance, though, there's a much bigger issue at play.

[QCtech]

2003-2004 completely different IAV. As per the manual and personal experience. 2003-04 IAV wont burn up your ECU like the 2001-02. And yes, 2003-04 is completely electric, no manual cables to the throttle body. I concur that his brakes are going out because of lack of vacuum. If he fixes his engine problem I dont think his brakes will keep failing. In any case, he should have new parking brake shoes installed and properly rigged to stop or at least slow down in case he have an emergency.

Could you tell me how exactly did your mechanic cleaned the throttle body? Did he just sprayed something from one side of the throttle body or did he actually removed the whole throttle body and carefully cleaned both sides? If he just sprayed something, your TB is still dirty on the other side. You need to remove it to carefully clean it properly. Otherwise it will look nice by the outside and have a wall of mud at the other side and you wont know.

When you turn on the AC if you have a dirty TB, your idle while stopped may go lower instead of higher and this will make the engine shudder. That is why the problem might be getting worst with your AC on. Also, did any of the mechanics you went to did the idle relearn? What is your idle RPM right now??
And where are you located? If you are not far from me, I could have a look and try to clean the TB properly and do the idle relearn.

[tee2]

Hey everyone,
Thanks so much, for all of those replies. I really was not expecting all of that. Alright, so down to business:
Buzzman-
Would I need to replace the IACV, or do you think that cleaning it, would make a positive change?
BarnaccleBob-
While the car starts to have a mind of it's own, I am positive that I am only hitting the brakes. Even when only applying the brakes, the vehicle wont stop, until it decides it's good, and ready.
1998Baja-
You know, I don't know when the last time that transmission fluid was changed, and that noise, seems as if it is coming from the front of the ride. I don't know if what i'm about to say makes a difference, but before buying the Pathfinder, I brought it over to the dealership, to get that pre purchase inspection completed. Before I brought it over there, I checked all the fluids, and it had plenty of bright red transmission fluid. When the pathfinder pulls out of the dealership inspection station, I am told by the dealership mechanic that the car has absolutely no transmission fluid in it. Later on that day, right before I cut the owner a check, and purchased the vehicle, I check the fluid levels one more time. Plenty of transmission fluid in there. Also, this pathfinder has been sitting outrside, for about a week now, and I have yet to see any sort of drip spots under it.
Atraudes-
When the Pathfinder starts to go nuts, I can push those brakes all the way down, and the it does not make a difference. I had my ABS system checked, and there wasn't anything wrong with it. The strange thing is, while this is happening, the pressure that I get from pushing that pedal down, feels exactly the same as it does when the car is functioning properly. It doesn't feel as if there is to much resistance, or not enough resistance. The car just doesn't want to stop. Kind of hard to describe, but it doesn't feel like there are no brakes. Even so, the car won't stop. I'm not sure how old the brake fluid is, but I know that the car has new pads.
BlindAviator-
That does make sense. Any idea what the culprit could be?
Qtech-
You know, that's a good question. I am not sure if he took it apart, or wiped it down. Tomorrow, I can ask him for some details. I know that none of the mechanics did an idle relearn, and I am not sure what the Idle RPM is. I will check, and post that info. I'm up here, in Northern CA.

Going by the responses, the problem could be within the IAVC, TPS, vacuum hoses, or the main computer. Does anyone know if there is a way of testing these components? I'm guessing that it would be expensive to start replacing components. Unfortunately, I do not have the budget to start throwing in new parts, while keeping my fingers crossed. That's why I am wondering if there is a way of testing these components first?
Thank you again, everyone. I'll get back to you, with that throttle body cleaning, and the idle RPM info.

[atraudes]

We love a good mystery

The EC section of the FSM starting on page EC-424 has some troubleshooting steps you can do on the IACV, and you can also pull it off to see if there's any coolant contamination. Vacuum hose are probably just best replaced as you see them (probably <$10 for all the hose you need), but you can inspect them by flexing them and looking for cracks or wear points. For the ECM, just pull it out and check for scorch points, blown capacitors, make sure it doesn't smell burnt, etc. Again, make sure you disconnect the battery while it's disconnected though.

What you describe with the brake pedal still feels like the ABS, though I don't have anything conclusive to back that up. I know you had it inspected already (independent shop, right?) but it may be worthwhile to have the dealership take a look as most smaller shops don't have the manufacturer's software.

No transmission fluid is pretty suspect too!

I still don't know what to make of it all, but starting with the basics and running down the list of the simple stuff could yield more clues.

[barnaclebob]

When it takes off, do you pump the brakes or just push hard? Since you don't know the age of the brake fluid you may want to bleed it just to rule something out that's cheap and easy to do.

[Blindaviator]

Also when you say the brakes don't work are you pushing as hard as you possibly can??
As Barnaclebob says try pumping the brakes as well??

If you are pushing as hard as you can and / or pumping the brakes to no affect then it could be the ABS interfering with the brakes??

Since you seem to have so many unrelated issues happening at the same time the only thing I can see that connects them all together is the ECM... If it was me I would try replacing the ECM just simply to eliminate that possibility... I haven't looked into prices of an ECM but like just about every other suggestion here it is a shot in the dark at trying to find the problem...

The no idle and / or dying suddenly is likely the IACV... I just dropped a used engine into mine and at first it was having issues idling after revving the engine (rev and it almost dies before it can get the idle right)... I am having a swirl control valve code which may contribute to it but mostly it is due to the ECM relearning after an extended time without power...

[QCtech]

All those things can be checked one by one with the service manual and a few devices. It depend on your skill level. The manual is here on the website in the manual section. What I still dont have clear about this problem from any of your posts is if the brake problem comes after the engine start dying out and if your engine dies out completely or just sputters, cough, etc. This is important because an engine that just dies would definitely point to the IACV. If at that moment you just hit the brakes, they will fell normal in that push, but they will probably stay down and take long to come back because the engine is not supplying vacuum. This is my best guest. If you want to totally troubleshoot this yourself and you have time, another car so you dont depend on this and a good multimeter and tools you might tackle this yourself but it will take some time. I suggest if you are serious about it, to buy the Nissan Data Scan 2 Software plus cable which I bought both for 60 dollars for OBD innovations. It will read all your codes including the transmission and abs ones, and will also erase them. It also have some functions that the dealership have like idle valve relearn, steering sensor calibration,looking at the trans solenoids operating and can program your immobilizer key if you get your pin number right. It have been of great help for both my Path 2003 and my infinity G35 2003. They also have a free version on the google app store that you can use to do the idle relearn with a 12 dollar ELM 327 from Ebay. All the info is on their webpage.

The IACV on the 2001 could damage your ECU. There is a service from someone and I think is right there in California that fixes the ECU for around 150 dollars, look for it on ebay or search the posts here. If your ECU is not bad then you could proceed to just change and relearn your IACV if properly cleaning it does not fix your problem. I dont know if it have been mentioned, but someone in the forums had his Path sputtering and it was the fuel filter that was clogged. The thing about not having trans fluid according to the dealer is weird to me, as well as having very red fluid in a high milleage trans, because it might point toward someone doing a recent trans flush before you bought it. When a trans flush is done is either because is due, or because the trans was slipping and they tried to correct it the cheapest way possible. The thing that most possibly wont show on a scan will be vacuum failures, so check all your vacuum system and PCV valve. Also, your vibrating noise, althoug I think unrelated to brakes, could be your exhaust pipes. There were known to leak and vibrate. Another thing that I did not mention before as it is a little far out, did you check the left forward wheel well to check for corrosion? There is a recall for that and in the worst of cases, the metal around the strut tower can collapse toward the inside and cut your steering ,etc etc. Keep us updated what you find.

[bryanmenard]

I know this is about a Pathfinder but, given our audience here, I want to clarify - just for the record - that the drive-by-wire throttle never made it to the QX4 for 2003. Neither did curtain airbags.

The 2003 QX4 was essentially a carryover of 2002.

I just wanted to put that here in case it was searched later because this thread has a lot of good information that people could use later. It's one of those QX4/Pathfinder differences that needs to be said, and resaid because of the IACV issue, which all 3.5 QX4's have

[Buzzman]

Hey everyone,
Thanks so much, for all of those replies. I really was not expecting all of that. Alright, so down to business:
Buzzman-
Would I need to replace the IACV, or do you think that cleaning it, would make a positive change?

There are a few of us that have been on here for many years, and like myself, have had our Pathfinders/QX4's for many years.
Example, I have been here since 2007, and have had my Pathy for 15 years. I know every nut and bolt on that thing.
All this to say that when I and others are urging you to replace the IACV, I would not hesitate much longer.
They are not cheap, but it is money well spent.
Cleaning a 15 year old IACV is probably not effective. I wouldn't bother trying.

[tee2]

Hey everyone,
I just wanted to give you guys an update. Ive taken this little beastie, out for a couple of nights on the back roads, trying to pisss it off, and see what makes it tick. Ive been driving at different speeds, trying various gears, and configurations. The AC, was still triggering the madness, but last night, the check engine light actually came on. Ive taken this thing to several different mechanics, but have only been able to play the guessing game. Seeing as the check engine light was on, I brought the Pathfinder over to my guy, and he was actually able to pull some codes this time. It turns out, the IACV is crapping out on me. Tomorrow, I'm going back over to his shop, and he is going to replace it. Hopefully after that, it's nothing but smooth sailing. I'll keep you guys updated. Thank you again, for all of the advice. Hopefully, this project will be over soon, and I'll finally get to enjoy this ride.

[Buzzman]

Hey everyone,
Seeing as the check engine light was on, I brought the Pathfinder over to my guy, and he was actually able to pull some codes this time. It turns out, the IACV is crapping out on me. Tomorrow, I'm going back over to his shop, and he is going to replace it.

Hopefully you haven't left it too late.
What are the codes?
When the IACV first starts acting up, you can save yourself a lot of grief by replacing it right away.
If you wait too long, the bad valve will take out your ECM.
That's what happened to me.
I took too much time guessing, troubleshooting etc., before replacing my IACV. By the time I did, the ECM was damaged.
I had to send it out for repairs. A major PITA.
This is why I was trying to encourage you to replace it.
Now that codes are being thrown, you may have left it too late.
One other thing: you'll have to do a re-learn after installing the new IACV.
Good luck.

[QCtech]

I advice anyone who plans to keep any of these nissan/infiniti vehicles from 2000-2007 to buy the nissan data scan 2 package. I dont work for them or am associated with them in any way, but this thing have saved me already over 300 dollars (or more) on having to go to the dealer to read my codes and do idle relearn and steering angle sensor relearn. it also helped me troubleshoot the wheel speed sensors while running the car and seeing all of them were reading correctly. It was only 60 dollars the software and cable from OBD innovations, and before I had a ELM 327 dongle(12 dollars) that you can use with their free lite version of the software and do the idle relearn. For me it have been money well invested, and if you know someone that needs a relearn or tcm,abs modules read out, you could charge them a few bucks and maybe even make some money. Just putting it out there in case it helps someone. In this case, if you had to pay for all the times you took your path for code reading, you already paid too much.Good luck.

[Buzzman]

I only have a basic code reader, which doesn't allow me to do a relearn or anything, but even with that, I've saved a whack of cash by scanning my own codes and troubleshooting with it.
I totally agree with you, regardless of what you drive. Get a code reader.

[tee2]

Hey guys,
I am not sure what the exact code was, but I do know that it was replaced. The car still drives beautifully, but I have been trying to complete the relearn process, for about 4 hours now. I will list the methods that I have tried, below. I hear what you are saying about the risks on waiting too long, to replace the IACV, but this Pathfinder has pretty much been parked for the majority of the time that I have owned it. I probably drove it just a very few small number of times, and when I noticed it acting up, I left it parked, until I brought it over, to get that IAVC replaced. Actually, during those small number of times, that I was driving it, most of that time was spent mechanic hoping. Hopefully, after this relearn, then I'll really be good to go. I made a call to the Nissan dealership up here, and spoke with the service tech. I got off the phone, feeling a little confused. He told me that the IACV, on the 2001 Pathfinders, is pretty much plug and play. He said that there is no need for a relearn. The reason that I am feeling confused, is not only because the below steps have not worked for me, but also because some folks are letting me know that I should relearn, and the service tech is saying don't bother, the Pathy runs extremely nicely, but the SES light won't clear. If you all could share your thoughts, I'd appreciate it. Steps tried, listed below.

1st tried:
1. Start engine and warm it up to normal operating temperature.
2. Check that all items listed under the topic “Preparation” (previously mentioned) are in good order.
3. Turn ignition switch “OFF” and wait at least 10 seconds.
4. Confirm that accelerator pedal is fully released, turn ignition switch “ON” (without starting vehicle) and wait 3 seconds.
5. Repeat the following procedure (5-a and 5-b) quickly five times within 5 seconds.
5-a. Fully depress the accelerator pedal.
5-b. Fully release the accelerator pedal.
6. Wait 7 seconds, fully depress the accelerator pedal and keep it for approximately 20 seconds until SERVICE ENGINE SOON stops blinking and turns ON.
7. Fully release the accelerator pedal within 3 seconds after SERVICE ENGINE SOON turned ON.
8. Start engine and let it idle.
9. Wait 20 seconds.
10. Rev up the engine two or three times and make sure that idle speed and ignition timing are within the specifications.

2nd tried:
Before performing Idle Air Volume Learning, make sure that all of the following conditions are satisfied. Learning will be cancelled if any of the following conditions are missed for even a moment.

Battery voltage: More than 12.9V (At idle)
Engine coolant temperature: 70 - 100 C (158 - 212 F)
Park/neutral position (PNP) switch: ON (Shifter in Park or Neutral)
Electric load switch: OFF (Air conditioner, headlamp, rear window defogger)
Steering wheel: Neutral (Straight-ahead position)
Vehicle speed: Stopped
Transmission: Warmed-up (Drive vehicle for 10 minutes.)
Procedure

1Turn ignition switch "ON" and wait at least 1 second.
2Turn ignition switch "OFF" and wait at least 10 seconds.
3Start engine and warm it up to normal operating temperature.
4Check that all items listed under the topic PREPARATION (previously mentioned) are in good order.
5Turn ignition switch "OFF" and wait at least 10 seconds.
6Start the engine and let it idle for at least 30 seconds.
7Disconnect throttle position sensor harness connector (brown), then reconnect it within 5 seconds.
8Wait 20 seconds.
9Make sure that idle speed is within specifications. If not, the result will be incomplete. In this case, find the cause of the problem by referring to the NOTE below.
10Rev up the engine two or three times. Make sure that idle speed and ignition timing are within specifications.

3rd tried:
1) Drive the car to "warm up" temperature. Make sure your idle is close to 700 rpm.
2) Ensure any battery draining devices are off. Ie. headlights, interior dome lights, HVAC, stereo.
3) Turn the car ignition key to "OFF"
4) Wait ten seconds
5) Turn the key to "ON" (not start)
6) Wait three seconds.
7) Perform the following five times in five seconds or less. Fully press the gas pedal and release.
8) Wait seven seconds from last of the five releases.
9) Fully press the gas pedal and hold down. Within ten seconds the "Service Engine Soon" light should begin to blink.
10) Wait another ten seconds (while still holding the gas pedal) and the "Service Engine Soon" light should stop blinking.
11) As soon as it stops blinking, release the pedal, start the car and check the idle (should still be around 700 rpm)
12) Let the car idle at 700 rpm or so for about 25 seconds, rev the engine a few times and then let it return to idle.
13) Shut the car down.

You car has now relearned the new air volume, which should be different than it was (stock). You may notice a bit of a rough idle for the next 20 miles. This is normal and will go away. The reason you should make sure idle is around 700 rpm (full warm up) is because the car measures the air curve in relation to idle, so you don't want to confuse it.

Also, I brought the truck over to my guy, on Friday morning, and he managed to clear the SES. Unfortunately, after a couple of errands had been ran, the SES came right back on. Still ran fine though.

[QCtech]

Your car wont relearn as long as you have an ses light on. That is one of the requirements to do the relearn. If the ses was cleared and then the relearn done and you are idling at the correct rpm,then your ses could be another thing that have nothing to do with your iacv. My advice stands on getting your own code reader that can read abs and tcm also.

[tee2]

Yes, that scanner is definitely something that I will need to get. I brought it down to the shop, and the SES code, came back as the mass air flow. My guy couldn't figure it out. He checked the mass air flow, and couldn't detect any issue. Is it strange that the SES light, relating to the mass air flow, appeared damn near immediately (a couple of times turning the Pathy on/off) after that IACV was replaced? Is it possible that it could be a glitch, of some kind? I have had cars with mass air flow issues, and they didn't drive as beautifully as this pathfinder does...the cars that I have had with mass air flow issues, would act up in similar ways that the Pathfinder did, before that IACV was replaced. Also, if it makes a difference, the SES light is solid, and not blinking.

[QCtech]

The MAF can be cleaned. If you had a very dirty and clogged filter a little cleaning might do away with it. Use only maf sensor cleaner or a similar quality product like LPS contact cleaner that wont damage the sensor or cables. I have not gone thru the 2001 wiring diagram and I dont think it have and IDPM so I can not comment of where your ses is coming from. I know that the IACV can fry something in your ECU and you will have some ses. There is people here that have gone thru it and may be able to tell you what codes they got when that happened. Otherwise, start with the cleaning, erase the code and test.

[Buzzman]

Could you post the actual codes for us please? That will help us.
A P505 or P500 code for example could mean the ECM may be damaged.
If your tech is telling you that you don't have to do a relearn after replacing the IACV, then it's time to find another tech.
You must do a relearn.
Now, having said that, I was not able to do a relearn myself using the method described in the FSM. It would never "take".
I also had an SES light after replacing my IACV and repaired ECM, but it was a code for high RPM's, not the MAF.
I went to my dealer where a tech did the relearn in 3 minutes with his scan tool (for free). The engine has run flawlessly for two years now.
Please post those codes.
Thanks.

[tee2]

Hey everyone,
I was able to clarify with my guy earlier today, on the codes. It wasn't the MAF. The exact code, is P0505 Idle Air Control System. He told me that the idle air control valve, from last week, could be damaged, and that he would be glad to replace it free of cost. As a side note, I managed to get the relearn completed at a shop, using a computer, instead of all that time consuming jazz that I shared with you. I honestly didn't think that the car could drive any better. I was completely satisfied with the Pathfinder's performance, after the IACV was replaced. However, after that relearn, that thing felt like I had injected it with steroids! I loved it! If you wouldn't mind, could you please share your thoughts on replacing that corrupt IACV? After the relearn, the SES light cut off. Unfortunately, it came back on after a couple of times turning the truck on/off. Thankfully, I don't have any of that bucking down the road/Pathfinder having a mind of it's own, like I did in the past. Thanks guys.

[Blindaviator]

Give it a week or so of driving and then try clearing the code again. After I did my engine swap a few weeks ago I had a lot of codes but After a day or two all but one cleared up.

Last code so far is the Swirl Control Valve which I didn't have before the swap.