Hi,

I hope someone can help me decide if I'm getting decent advice from the dealership. Last month my 02 Pathfinder (155K) started to stall every few trips (always at idle speed or very close to it). It would always start up immediately after that. No codes. The 1st mechanic replaced the crank shaft sensors and cleaned the gummy idle air control valve. He mentioned fuel pressure was low and maybe the fuel pump should be replaced if the stalling continued.

It continued to stall. I cleaned the MAF sensor, replaced the fuel filter, and put in a new fuel pump. Still no OBD codes.

The stalling became more frequent, and then the car would crank but not start. I had it reluctantly towed to Nissan, where they put in a new IAC valve and cleaned the throttle body. The tech noticed coincidentally that the alternator was on its way out (a new development). At this point I was already in $600 for the IAC valve, and was torn about whether to keep going or get rid of the car, but OK'd the new alternator.

Picked up the Pathfinder this morning for $1500, started it up in the lot, and my RPMs were idling all over the place. The tech heard the commotion, walked over, and told me that he thought the front desk had let me know -- the Pathfinder wouldn't complete the idle air relearn procedure. That means ECM replacement. My stomach sinks.

I won't pay for a new one in a car this age but I'd consider a $250 circuit board repair. My issue is that in other posts when an IAC valve took out the ECM, people commented that that the ECM stinks when opened and usually has a burn path. Mine has no odor and looks pristine. It also doesn't have the characteristic P050 code - I only have P057 (idle too high).

Any advice? I've tried doing the idle relearn myself 3 times and will probably try a few more before calling it quits. Send in the ECM anyway to have them do a diagnostic? Feeling stuck and kicking myself for not cutting my losses $1500 ago. It's just that the Pathfinder had been such a solid car for all those years . . .

Thanks in advance.

I feel what you are going through...and this is the main reason, many years ago, I decided to troubleshoot and repair my own cars and truck... The dealer made the most damage to you and the trust you had in the truck.. The cam and the fuel pump were not necessary... The IACV issue is a not a common one but it is known that once the IACV goes, there is a reason for it and usually is the ecm... These trucks are a thing of the past (reliability speaking)... My 2001 at 260K still has the original starter,alternator,engine and transmission... The body is rusting away, and I will have to let it go soon... I bought a 2003 for my wife...This thing is a dream.... Compared with a pickup I also have, which is a gmc 1500... money pit...

Anyway, all this to tell you that a few guys in here and other forums had good experience with the 250$ repair you are taking about... Investing another 250$ for this truck is worth it... You have at least another 100k to do with it.. Too bad you can't just go back to the dealer (guesser) and tell him to take back the cam and fuel pump and give you your money back...

fleurys wrote: The IACV issue is a not a common one but it is known that once the IACV goes, there is a reason for it and usually is the ecm...

Actually, from what I have read on here it is a common issue for the IACV to fail which is likely due to a coolant leak due to the rubber gasket failing in the IACV, which then in many cases but not always will short out the ECM.

You are saying the ECM is taking out the IACV which is not the case, it is the other way around.


This is the rubber gasket that frequently fails as the vehicle gets older / mileage increases.

https://www.vividracing.com/catalog/-p-151397452.html

Good point...

As for common or not, I've had 3 pathfinders up to now all in their 200k plus and none of them has had this problem...

It's all good..

BackToFrio wrote: My issue is that in other posts when an IAC valve took out the ECM, people commented that that the ECM stinks when opened and usually has a burn path. Mine has no odor and looks pristine.

https://www.youtube.com/watch?v=sVE93cOMz9s



You can see here, this is actually from a Maxima forum which also has the same issue with the IACV / ECM.

This is the chip that is damaged.




This is the best price I have found for the ECM repair

http://www.ebay.com/itm/INFINITI-QX4-En ... sQ&vxp=mtr

I really appreciate the rapid responses fleurys and O4pathse. That's a great photo. I was really hoping that my ECM would look like that and therefore be obvious that I was on the right path. Mine is spotless inside. Or at least give me the predicted P0505 code (which does has a faulty ECM as one of its possible causes). Then I'd be more inclined to trust the recommendation of the Nissan tech to just replace it.

Unfortunately I only have the high idle code (P0507) which doesn't list the ECM but has a bunch of other causes like vacuum leaks, PCV valves, and EVAP systems. I'm really lost here. I wonder if it's possible for the ECM to fail but not have damage visible to the naked eye. Thanks guys.

I'd be inclined to test your IACV resistances. It is possible for a soft failure on the IACV to affect your idle.

I had the IACV->ECM failure, replaced the IACV, had the ECM repaired. But not too long afterward, my Pathfinder started stalling at idle and registered a P0505, and I found the resistance values of the IACV solenoid to out of (lower than) spec described in the EC manual. I believe the lower the resistance of the IACV, the higher the chance of damaging the ECM. Replacing the IACV again corrected the problem. You may have to remove the IACV solenoid to test it.

Reading on P0507 suggest a massive intake leak in order to prevent the ecm to adjust the idle.. Did you do visual inspection of a possible huge leak after the MAF ? If so, then I would start diagnostics on the voltage coming in the IACV... Also checking the resistance to it... Now if it is the ecm, I'm reading everywhere that the IACV should be replaced before pluging the repaired ecm... I fear that if it is your ecm, that the new IACV might be damaged.... So you need to check the voltage and resistance to it...

Do you have a FSM (Factory service manual for your 2002 ? There is a good troubleshooting procedure for the IACV on page EC 459..

Basically, from what I can understand, the idle is controlled by the ecm using multiple sensors data... In the end, the ecm is sending the signal (voltage) to the IACV to control the idle.. From there you can either determine that the IACV is bad (with the resistance test) or that the ecm is not sending the signal to it. Even if you decide to take the plunge with the ecm repair, you will have to make sure that your IACV is not damaged before re-plugging the repaired ecm...

One more thought... I would write to the repair company in order to know if they are able to tell you if the ecm is damaged or not... You can tell them about the lack of visual cues and maybe just work a pricing with them to just test it... If nothing is wrong then you have one less thing to worry about and probably just have to pay shipping... I would definitely talk to these guys as they see many of them (ecm) in a year...they will know...

If you end up sending your ECM to get fixed, I had mine repaired by a seller on ebay called modulerepair (listing here) for about $200 using next-day shipping. They called me and let me know everything tested fine and they'd let me off the cost if I wanted, but I elected to have it repaired anyway since I was already in for the shipping and downtime.

When I had a problem with a suddenly high and erratic idle the TPS (throttle position sensor) had gone bad. It was revving the engine up over and over and the idle was really high, maybe around 1500-2000 rpm. It's a cheap part; I'd replace that first before anything else. Just make sure it's properly calibrated after installing. There's a procedure in the FSM on how to do it.

If your ECM looks fine, it probably is.

Can you call up the dealership and ask how they tried to do the ECM relearn, and how the Pathy 'could not complete it'? I was under the impression that they can do the relearn with their computer system, and it takes them five minutes.

My guess is that they're trying to suck more money out of you. I suspect this is what happened with the alternator.

The relearn is kind of tough to get down - open up the FSM and follow each instruction to the letter. In my case, I could not get it to work because I did not drive the car for ten minutes prior to performing the relearn procedure. Surprisingly, this a necessary step, and the FSM states that the relearn won't go through unless the entire procedure is followed to the letter.

Finally, I found a seller on eBay that fixed my ECM for about $70, should you decide to go that route. They were quick and good. Look up my post history for their info.

Good luck.

I am dealing with a relatively simular aet of issues. Can anyone who has dealt with this advise?

Had no issue prior to the following:

Last week I replaced the Valve cover gaskets, throttle body gasket, and upper Air Plenum gasket. During this repair I had to remove pretty much everything from the valve cover gasket up... As a side Note the TPS sensor was replaced withing 6 months, all new plugs, oil change, cap, rotor and wires....After reassembling everything the truck drives well but once warm it surges at idle.... And if in gear almost and has stalled on me.. Starts right back up... Still surges..

I cleared codes, drove it some more and I am getting a misfire on 1 or more cylinder code, as well as the P0505 code which led me to recheck all the vacuum connections as well as Iavc power plug which all seem connected fine.

Any thoughts or suggestions what to check next would be HIGHLY appreciated... Thanks

atraudes wrote:If you end up sending your ECM to get fixed, I had mine repaired by a seller on ebay (...) for about $200 using next-day shipping. They called me and let me know everything tested fine and they'd let me off the cost if I wanted, but I elected to have it repaired anyway since I was already in for the shipping and downtime.

When I had a problem with a suddenly high and erratic idle the TPS (throttle position sensor) had gone bad. It was revving the engine up over and over and the idle was really high, maybe around 1500-2000 rpm. It's a cheap part; I'd replace that first before anything else. Just make sure it's properly calibrated after installing. There's a procedure in the FSM on how to do it.

Thanks to everyone above for the advice. I have double-checked the replacement IACV, seems to be in good shape but still no luck with the idle relearn via Consult at Nissan or here manually (and I did heed the minimum 10 minute warm up drive). The car drives, no recent stalling, but the idle is erratic (fluctuates dramatically at start-up, then "normalizes" to about 1100 RPM during the trip with dips to 500 RPM at lights). I'm left with the codes P0506 and P0507 (idle too low, idle too high). I think the next step is to send in the ECM for repair.

The vendor in the above post requires not only a new IACV but a TPS to issue a warranty on the ECM. I see that the TPS can cause similar symptoms, but mine checks out according to the FSM and my multimeter. Can it still be acting up? Is it obvious (electrically) when it fails? I think it's a $60 part so if it's worth replacing regardless of my tests results I can do it.

I really appreciate the help. Many thanks.

*RESOLVED*: I had my ECM repaired and the car is now fixed. If anyone else wonders, as I did, if the ECM could be damaged despite any obvious burn marks/odor -- the answer is apparently yes.

I followed the recommendation from one of the above posts and used Module Repair Pro in Van Nuys, CA (via the eBay listing link). The price was $95 and they tested/repaired/shipped back out to me the same day it was received. Performed the idle relearn procedure and the car is back to normal.

Thanks again to all who responded.

Great news ! Thanks for updating the post !