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  #1 (permalink)  
Old 08-25-2007, 08:05 PM
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Default Maxima 01, P0505 IACV...

got a car that has had a P0505 code for a while now. The rpms would go up and down when idling, car surging when driving, just like in other posts. Doing a P0505 Malfunction A and B test according to the Service Manual, the code would always come back doing a B test. Unfortunately, the car was driven with a bad IACV for a while, and finally this week got a new IACV(from salvaged car), but when removing the old IACV, the harness was a bit melted together, and after some work was unstuck from the IACV.

With the new IACV valve installed(including the metal body into which the IACV is inserted), the car does the same thing, idling up and down, and Malfunction B test lights up the code after the reset.

In addition, i've checked for continuity between 4 ECM wires going to the IACV harness, and the 2 wires supplying 12v to the harness, and all wiring is good. When doing the vacuum test, with the wheel turning and not, there is vacuum. Resistance between valve connectors of 22ohms is all good.

Reading about IACV going bad and burning of the ECM may explain the melted harness.

In light of that scary thought of ECM being shot, i have few questions to determine what to do next:
- What are the electric motor mounts, and where are they? (the culprits that started this whole problem). What to do with these mounts? I've searched the Service Manuals for that term, and it must go by a different name.
- IACV air volume learning...can i do that? Or can the dealer only do that, is it worth the shot to do the learning before replacing ECM based on the facts stated above?
- Can i test with dvom to see if ECM is fried?
- Can the car be driven at this point with new IACV valve, removed mounts(if i unplug them), and potentially burned ECM?

You help is greatly appreciated.
Thank you.

Enso~
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Old 08-26-2007, 04:31 AM
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First thing you should do is unplug the front and rear motor mounts. The connectors are brown. Both should be located neat the transmission bell housing where it meets the engine block. One is near the front and the other is a little higher. After that you will want to relearn the idle air volume. I have always done it with a nissan scan tool so I don't know if it can be done without it. If the relearn does not work the next step would be to replace the ecm. You can remove the ecm and the cover and sometimes see where the circuit is burned out.
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Old 08-26-2007, 09:12 AM
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Thank you for a quick reply. Do i unplug the engine mounts and leave them unplugged permanently? Or do i plug them in after the IACV issue is fixed. If they will be unplugged, will that set another code in ECM.

Can you please confirm that these are two connectors you are referring to...

Thanx alot!
Enso~
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Maxima 01, P0505 IACV...-mount.jpg  
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Old 08-26-2007, 10:07 AM
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Quote:
Originally Posted by EnSoNiQuEs~ View Post
Thank you for a quick reply. Do i unplug the engine mounts and leave them unplugged permanently? Or do i plug them in after the IACV issue is fixed. If they will be unplugged, will that set another code in ECM.

Can you please confirm that these are two connectors you are referring to...

Thanx alot!
Enso~
Yep, those are the ones. Leave them unplugged. They don't set codes and you won't notice any difference.
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Old 08-31-2007, 06:46 PM
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Thanx for the reply and all your help in pointing me in the right direction to resolve this saga. I've finally had a chance to unplug the two engine mounts and do more testing with ECM. Interestingly, with engine idling, the voltage on the 4 wires at the ECM side were 14v. No fluctuations in voltage, which should have been occuring between 0.1-14v. When removed the ECM, and opened the lid, voila!..the small,black, rectangular component, standing upright on the ECM board, was actually cracked in half and meltdown from the ECM was covering some of the electrical pathways, leading to the pin 6,7,8,17 of the ECM.

Now i've got to find a used ECM since the car is over 5years/60k. When the ECM gets replaced, is IACV learning mandatory?
Anyone know of a good place to get a replacement ECM?

Thanks again.
Enso~

Last edited by EnSoNiQuEs~; 08-31-2007 at 06:48 PM.
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Old 09-01-2007, 05:55 PM
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Quote:
Originally Posted by EnSoNiQuEs~ View Post
Thanx for the reply and all your help in pointing me in the right direction to resolve this saga. I've finally had a chance to unplug the two engine mounts and do more testing with ECM. Interestingly, with engine idling, the voltage on the 4 wires at the ECM side were 14v. No fluctuations in voltage, which should have been occuring between 0.1-14v. When removed the ECM, and opened the lid, voila!..the small,black, rectangular component, standing upright on the ECM board, was actually cracked in half and meltdown from the ECM was covering some of the electrical pathways, leading to the pin 6,7,8,17 of the ECM.

Now i've got to find a used ECM since the car is over 5years/60k. When the ECM gets replaced, is IACV learning mandatory?
Anyone know of a good place to get a replacement ECM?

Thanks again.
Enso~
ecm coverage is 8 years or 80,000 miles. If you are over that check Car-Part.com--Used Auto Parts Market
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Old 11-01-2007, 06:54 PM
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Thank you for all your help. Finally got a new ECM for $100, brought a new computer to the stealearship and said, here is the new computer, asked to reprogram the keys and possibly check if IACV needs to be re-learned since I've just replaced it. Got called back, they spent two hours analyzing the "problem", that the car was idling erratically, and they didn't need to reprogram the keys! and said i needed a new IACV harness replaced (they saw the IACV harness a bit melted, which i've checked with DVOM to be ok) for a wonderful $1700!

The original request just to reprogram the keys was completely ignored! (Reason was that they can't expect every customer to know and tell them which part to replace...lol! so the smart fella at the front desk wrote up the service request, what he thought should be done, not what was asked!)

Getting the business manager, 2 techs, and the "smart" fella in one room, explained the P0505 saga and told them, all i want is keys reprogrammed! They reluctantly said, ok if that's what you want.

Put the new computer in, they reprogrammed the keys, and the car is idling ok now. Surprise, surprise:-)...all for $90!. Will keep an eye on it for a few days. Phew...i can only imagine if I wasn't helped here by you folks, how they'd fleece me for tons of money!

Once again, thank you!

I'm just curious if any of these ECMs get rebuilt, or its junk. Here is a pic of the burnt out part due to engine mount/IACV P0505 code:
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Maxima 01, P0505 IACV...-p0505.jpg  
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Old 04-05-2011, 05:04 PM
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How can i find a used ecm that matches mine. I don't want to pay $1000 at the dealership. Is it possible. I have a 20th ann. Edition
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Old 04-06-2011, 07:37 PM
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Quote:
Originally Posted by mrdeshone View Post
How can i find a used ecm that matches mine. I don't want to pay $1000 at the dealership. Is it possible. I have a 20th ann. Edition
I paid $1,200 for my car when they replaced the ECM at mid city nissan in Chicago. I think my ECM failed when I have 120k and they told me that warranty for the replacement is only 1 year or 12k miles. They advise to change the ECM and then the air sensor as well at that time.

My advise, do it in the dealer.
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