No. As the ECM says, you should check that continuity exists between the following terminals:

• ECM #6 - IACV#1
• ECM #7 - IACV #4
• ECM #8 - IACV #3
• ECM #17 - IACV #6

Here, "continuity" means "zero resistance between the two terminals".

 

Ok so I'm just testing the harness itself. TY

 

The IACV chip got damaged again, this is what the Modular shop just told me. He said there is a short somewhere.

Even with a 7.5a fuse the chip got damaged. Can someone give me any ideas to where to start?

 

you said before they used a different chip the first time- maybe tell them to use the correct one?

 

Yah true, its up to them what chip they use, they said they repaired over 40k of these Nissan ECMs. I'll wait till they send it back and see what happens I guess.

 

yeah i'm sure they would know better than i do, just thought it might be a starting point. if it didn't function the same as the old one surely it could cause problems and get damaged

 

Tell them to use a STA508A chip. It is a 120 volt 6 amp constant, 10 amp pulse.
The standard STA509A chip is a 52 volt 3 amp constant, 6 amp pulse.

http://www.alldatasheet.com/datashee.../STA508A.html?

http://www.alldatasheet.com/datashee.../STA509A.html?

 

Thanks for the suggestions, but I'll let them figure it out and see how it goes.

I just wonder where the short could be if the IACV harness is giving out 12v to terminal 2 and 5 each.

 

That's too bad (that it got damaged even with the 7.5A) fuse, but this is useful input for all of us. The STA508A chip suggested by Dennis can withstand higher current (10A pulsing, 6A steady-state), so my feeling is that the 7.5A fuse should be able to protect it. Let us know how it works out for you. (And don't forget you need a new IACV .... that's why the transistors are blowing up).

 

Whats the chances of the ECM harness being bad?

 

As a rule, harness failures should not happen much, if at all. Harness is a "passive component" that can be only damaged by excessive force such as cuts or rips, or by chemical/heat/other damage to the insulation. And you can check it - it's easy to check for shorts (to ground, or to power).

 

So the guy got back to me and said the same 2 middle transistors burned again on the new chip he installed. He even wants me to pay full price again for the repair. I might have to get ebay involved if this fool wants me to pay again.

 

How do I check for shorts to the harness?

 

To test for "short-to-the-ground": You take an ohm-meter (or multi-meter, set to measure resistance) and connect one of its probes to ground, and the other one to the first pin of the harness. If the meter shows zero ohms (or something close to it), label that pin MIGHT_BE_BAD, otherwise it's good. Repeat for all pins in the harness connector. Then:

• For every pin in the MIGHT_BE_BAD set: Consult the circuit diagram and/or the FSM, and decide whether whether the ground (i.e., the low/zero resistance measured) is legal or whether it's a failure condition.
• To prevent your ohm-meter from being damaged, always measure the voltage between the two pins before measuring resistance, unless you have a self-adjusting meter (so, this is BEFORE, not THEN).

So, it's quite simple if it weren't for the precautions you have to take so as not to blow your meter up. And the fact that you have to consult the FSM. Such is life.

The procedure to measure "short-to-power" is similar, but there is perhaps even more emphasis on measuring any voltage differential (in the 2nd bullet) to avoid blowing up your meter.

 

Thanks for the info maxiiboy. But man thats a lot of work tho. Not sure if I need to do all that. My car actually works fine, its just the idle problem.

Also, when I checked continuity for the harness:
ECM #6 - IACV#1
ECM #7 - IACV #4
ECM #8 - IACV #3
ECM #17 - IACV #6

I got OL meaning no continuity for any of them. I feel like I'm doing something wrong here. Thoughts?

 

The OL reading is good for a short circuit test but not for continuity. Continuity should be zero ohms (or maybe a fraction of an ohm).

The dictionary definition of continuity says that something is continuous from the beginning to the end. For electrical work, continuity just about always refers to the wiring. And in this situation it does. You want to disconnect the wire harness connectors from both the IACV and the ECU and check that the wire is not broken - that it is continuous, meaning that electricity can flow from one end of the wire to the other. Connect one probe of your ohmmeter to the IACV end of the wire and the other probe of your ohmmeter to the ECU end of the wire. If you have continuity, the ohmmeter should read zero ohms.

 

I was doing it wrong. Thanks Dennis.

 

Great string of responses on the P0505. I replaced my ECU and IAC last year. Now I'm getting this code yet again. sigh. A couple questions. If I have the ECU repaired, the company says they will flash the ECU as well.

So, if I put the ECU back, it will sync with the ignition key chip.

Here's the question: Does the IACV and the Mass Air Flow have to be flashed or synced with the ECU. One dealership here says the ECU will automagically recognize the new IACV and the new Mass Air Flow unit. A second dealership says no, I'd have to reflash / program the ECU. A third dealership mechanic says he doesn't know... just try it.

So, does anyone know if IACV, MAF have to be reprogrammed with the new ECU?

Also... what's the story with the motor mounts? That seems reeeeally odd.

 

"So, does anyone know if IACV, MAF have to be reprogrammed with the new ECU?"
- i don't think so.

"Also... what's the story with the motor mounts? That seems reeeeally odd."
- if you have an auto transmission, its advised to unplug your motor mounts. Motor mounts will take out your ECM if they go bad. There's a front and back motor mount.

 

No, neither the MAF nor the IACV has to be reprogrammed - the simple reason being that neither can be programmed, period. Second, if the question you really wanted to ask was "does the ECU have to be reprogrammed after a new MAF/IACV was installed" then the answer is also NO, at least on the 2000 and 2001 Maxima. At most, an overnight battery disconnect will solve any adjustments problems, as the ECU will re-adjust on its own.

Re. motor mounts: Yes, if your electronic engine mounts fail, they can fry your ECU. What's so confusing about it? I tried to explain it all here: https://drive.google.com/file/d/0B6O...ew?usp=sharing.

 

My harness continuity for both ecm and iacv terminals are good. The diagram on the FSM is actually backwards from the harness itself. I was testing the wrong terminals on the ECM the first couple times, thus, getting the OL reading.

edit...

 

I installed the new hitachi IAC and it worked. The idle is about 780mph on P/N. I didn't have to do the idle relearn.

So I would also recommend before installing everything to make sure the motor of the IAC is actually functioning properly. The aftermarket IAC wasn't doing this. I also added gasket maker when I installed the IAC to the Throttle Body.

Just under $300 total for repairs. And no dime to the dealership. lol

 

Congratulations, and we have a happy end! Hopefully, you have learned something. (Tell us what).

Now, I would ask you for a bit of feedback: Earlier, you said that the 7.5A fuse did not protect your ECU. On second thought, perhaps it did; yes or no? Just in case you are not sure, answering the following questions might help:

• You had both the bad IACV and your ECU in the car at the same time, right?
• Your ECU was NOT damaged, right/wrong?
• If the ECU wasn't damaged, something protected it. What/who was it?

I appreciate your feedback. My goal is to help people like you, and to prevent the propagation of misinformation. Thanks!

 

I'm not 100% sure if it was the aftermarket IAC or the ECM's fault for the blown 7.5A fuse. I just don't know.

I did return the ECM back to the person who fixed it and he said the same 2 transistors were blown again. I checked the ECM before I sent it back to him but visually I didn't see anything bad or didn't smell a burnt smell. He could have been lying to me and just wanted to double charge me for another fix.

I did check off everything on the FSM and everything checked out fine. Starting on page EC-433.

The most important thing is to check the continuity from the ECM harness to the IAC harness. And to also check if the motor is moving before install. If its not moving, its obvious the idle will not be correct because the air will just pass through.

 

Deja Vu!! Checkout the following post---->https://maxima.org/forums/5th-genera...d-seconds.html

The fix will seem straight forward once you follow Nakis through the thread. I did the following: This is a copy of an email I sent to NAKIS-you need to read his post carefully! Otherwise you will continue to fry IACVs and ECMs! The most critical step other than the obvious part replacement are the directions on page EC-111. YOU MUST HAVE THE TECH DO THIS PRIOR TO REKEYING AND STARTING THE ENGINE. Here it is.....To NAKIS:
Thank you!
I have a 4/2001 with continuous IACV valves replacement for years and a couple ECM's and my last "fix" with this issue was to close out the throttle with the idle screw and it worked for a couple years. Finally stumbled on your thread or odyssey with the ECM short and your thoughts about TSP and coolant problems in conjunction with the IACV. A week ago the Maxima fried the ECM and IACV. OBD codes 505 and 612 (dead ECM lots of carbon on the cover plate and at least 4 circuits burned through the 509 was melted) and another for the fuel regulator. I replaced the IACV, disconnected both EC motor mounts and bought a used matching ECM (EBAY which looked totally rebuilt on the inside) took it the dealer for rekeying with instructions.-----> top of the list requiring the TECH to follow instructions on EC-111 before reprogramming. Had a 21 year TECH on it and it took him an hour or less to close the throttle, rekey, and perform idle relearn. Good to go!
Thank you

Hats off to Nakis, et al

**Posted on the "coolant bypass thread"---->Just completed it today and I live in a fairly cold clime in N. IL and will report if any issues. But I view this as additional insurance against coolant contacting IACV. I have found corrosion at the pin base of at least 2 IACVs that have faulted and possibly a third to not closing TSP before starting.
Procedure: Purchased 5/16" brass split hose mender with the claw backs. Disconnected each hose from each side of the IACV/TB and joined each to the brass mender and clamped with existing. Capped each IACV port with 3/8" ID black chair tips and these aren't as snug as I would have liked but not certain I even need any but it looks more finished. Fired up with no issues. Maybe $3.00 with Cook County tax and might have saved me real money if done sooner. Ignorance isn't bliss! It's expensive!
Last edited by Darkrock; 11-02-2011 at 10:32 PM.



What will burn your *** is when find out the IACV are pure crap! I completed the above and a few months later it started all over again. Pulled the IACV and found it tested the 22-23 ohms on the pins and missed CONTINUITY ON THE SAME PINS RIGHT OUT OF THE BOX. I rejected 2 at the dealer that tested for resistance but missed continuity.

IACV Oversensitive or Underlying Design Fault
On 1/09/2012 daughter breaks down in Maxima and I go to fetch her and "it" hopefully. Cold starts fine and idles at 7-750 and I am thinking a bad batch of fuel. Until "it" warms up and the throttle commences to surge on warmup while running up the Stevenson at 12am and it doesn't like 2000rpm at all. Drives better over 2k than under 2k and at idle "it" is high at 1500rpm. These symptoms remain...Cold start and idle are in spec ...until "it" warms up...Surging (2-3K) at idle and running and when not surging a high idle of 1500. There are 2 codes for the dreaded P0505 and thi8s cannot be...
1. This is a 2001 A/T GLE and "it" eats IACV! In Fall of last year "it" ate another IACV and an ECM and I documented the repair under the thread ECU Fried In Seconds post and finalized with a Coolant Bypass of the IACV. It cannot be the IACV at fault it is now bullet proof...with the repairs I made.
2. I run through the litany of EC faults in my head and decide to do an Idle Relearn. I do it several times NG.
3. Break out TunerMax's checklist and start going through it and I am testing the IACV and each of the 6 pins are between 21-24ohms. Note I did not check CONTINUITY!
4. Decide to retune the TSP by using the .05 & .15mm gap at cable and multimeter at lower set of pins. Finally get it done. TSP relearn done. Same symptoms remain and I pull the IACV out again and check the pins which all test within spec. But this time I check CONTINUITY AND PIN NUMBER 4 MAKES A SLIGHTLY DIFFERENT SOUND! Note the ohms are all in spec at 21-24ohms.
5. Return it to AZone check the new one in the store for resistance and continuity and reinstall it with TSP retune and it purrs very nicely. Maybe 6 hours of actual frustration to correct it back to normal. What is there in this design that has such little tolerance for error? Sorry just a little rant!

**It has been about 3 years since the last "fix" it runs great ever since. Usual maintenance repairs but no issues with the idle. Knock on wood! Not bad for a 14 year old car.

 

Well, it looks like the 7.5A fuse did not help, at least not in your case. Thanks for your input!

 

Hello I need help ... please
have a 2001 maxima with PO505 code

 

The P0505 code is the IACV (Intake Air Control Valve). You can test it with an ohmmeter, following the directions in the service manual on page 436.

link to manual - http://boredmder.com/FSMs/Nissan/Maxima/2001/EC.pdf

This has been discussed many times, so if you search for P0505, you will get a lot more information without waiting for someone to answer you.

 

You have a bad circuit with the IAC to the ECM. I suggest you to not drive the car. Take out the IAC and replace it with a new OEM Hitachi, it costs around $130. Your ECM needs to be checked for burnt transistors.