Code P0505 caused by Engine Mount?

[plundccre]

I have been trying to source the cause of my P0505 code on my 2001 QX4 2wd. Every time I clear the code, I drive it around to reset the ECM. After about 120 miles or so the P0505 code comes back on. This has been preventing me from getting my smog certificate her in CA and I haven't been able to register the vehicle in over a year.

The IAVC was replaced. I suspected that I had blown the chip on the ECM and sent it in for repair to a source I have used for electronics on several cars. He could not find anything wrong with the ECM. He had it for a couple of weeks and everything tested good.

What he told me was something that I have never heard of and have not been able to verify so I am hoping for some help here. What he said is that certain Infiniti/Nissan vehicles have an electronic engine mount (that adjusts its stiffness depending on RPM) that when it fails, can also give the P0505 code. He said that you can rev the engine to about 3000 rpm and then unplug the mount. this will lock it in a stiffer mode and, with it unplugged, it will no longer cause the P0505 code.

Does this make sense to anyone? Is there an electronic engine mount? When I look at a parts diagram, I don't see anything electronic. Just a mount with rubber and 3 bolts.

I would love it if the fix was this simple and c heap. Any thoughts?

[mdmellott]

There is no active motor mount on your QX4. Even if it did exist on some other vehicle, it makes no sense that would have any effect to flag an idle air control valve or circuit fault DTC code P0505. Since you replaced your IACV and had your ECM checked, it is likely the issue is caused by the IACV harness connector or wire damage and/or IAVL calibration is out of sync, or there is a vacuum leak.

[plundccre]

Thanks. That makes more sense to me. I could not find an electronic mount on the car, and I also thought it suspect that one could cause a p0505 code. I drove the QX4 today, reset the codes and the p0505 came right back up again.

[Buzzman]

Thanks. That makes more sense to me. I could not find an electronic mount on the car, and I also thought it suspect that one could cause a p0505 code. I drove the QX4 today, reset the codes and the p0505 came right back up again.

Did you do a reset/relearn after the parts replacement? You have to do that or the code will come back.

[plundccre]

I followed the procedure that I saw online but I still getting the code. I also did a visual inspection and don't see any damaged wires or leaking vacuum from a visual check. Is there any kind of order of priority that someone could suggest to work through for the 0505 code?

The QX4 runs fine. No issues other than the code but in California we have to pass a smog inspection to register the vehicle. This problem has been going on for 3 years now with no registration. Obviously this isn't my top priority vehicle but id like to get it sorted out and with values on these, its probably not worth the expense to take it to the dealer to sort out.

[Buzzman]

The relearn procedure online is sketchy and doesn't always work.
I couldn't get my Pathfinder to "take".
I went to the dealer and the tech did the relearn with his scan tool in less than five minutes. Problem solved.
Didn't charge me anything either.
Probably wouldn't hurt to have them do it, even if it costs $20.