jcd2

Hello,

. I bought a 2001 Nissan Maxima SE with 212K miles back in August. When I'd come to a red light the rpm's would go from 800 then to 1100 back and forth. In November I was on interstate and it accelerated by itself. In patk the rpm's fluctuated between 2,500-3K back and forth. I replaced the IACV with an Hitachi OEM part. I borrowed a snap on scanner and the codes that appeared were the dreaded P0505(IACV fault), P0325 (knock sensor code), and a P1140 (EVAP small leak).I sent my ECM to Circuit Board Medics and it did have a bad chip. I recieved it today (1-21-17) and installed it and did the IACV re-learn and although the fluctuating idling isn't as severe in park; it still revs back and forth between 1500 & 2000rpm. I drove the car a few miles to Auto Zone and had my codes scanned and the only code was P1610 (NATS failed to initialize. I'm fairly certain this code was due to trying the re-learn several times. What do I do next? I can't just take the car to a dealership because money is extremely tight and I only paid $1000 for the car. Any help would be appreciated.

mydecember1985

iTrader: (1)

Did you replace the ECU and the IACV at the same time? There's a recent thread mentioning something about that if one is bad, it causes the other to fail. Bad IACV killed your ECU. Replaced IACV. Dead ECU kills new IACV. Replace/repair ECU and your dead IACV kills the ECU again.

Child_uv_KoRn

iTrader: (7)

Fried ECU can't kill IACV (power is cut when it fries the chip).

Pull battery for a while to reset, then retry relearn if needed.

maximatech12

Why can't you figure it out yourself just unscrew the cover and look at it. Take a multi-meter and test continuity within the chips.

jcd2

the chip was bad. That's why I sent it to Circuit Board Medics to be repaired. They sealed the ECM for warranty purposes. I'm not getting the 0505 code but the re-learn isn't working. That's what I'm trying to figure out. What do I do next.

cornholio

iTrader: (1)

^^ OP try this if you haven't yet

and ignore anything this guy post on here

jcd2

I will disconnect the battery and try that. Thank you all. So I won't clear any codes, I'm going to borrow a snap on scanner first and double check no tell tale codes.

jackman

Not if the burned FET is shorted. That's one of the possible failure modes for a burned semiconductor, and in this case, that would place continuous 12V across the IACV. I don't know if that will overheat the coils, but it will be powered.

Child_uv_KoRn

iTrader: (7)

But how long can that last before it burns up the traces?

It just doesn't seem likely to me.

Cephyr13

I just dealt with this issue. It's a common issue with these cars. The idle air control valve (IACV) leaks coolant and shorts out. This causes the car to idle high trying to compensate for it. It puts too much current through the ENG CONT1 circuit that goes to the ECU. This, in turn, fries the STA509A chip in the computer.

So if you have the computer repaired, but you don't repair the IACV, your computer fries again. And if you have the IACV repaired without fixing the computer, it fries the STA509A in the computer again.

Solution:

1. Replace your IACV value and bypass it with the coolant lines (just connect the in and out coolant hoses that go into the throttle body so coolant is rerouted around it--this is an important step to prevent the IACV from dying again).

2. Have the computer fixed with an STA508A transistor array chip instead. It handles twice the current of the stock STA509A chip. (I needed this quick so I got the computer out of a junkyard and used one of its other STA508A chips found elsewhere on its board--don't use the STA509A chip on the board because there's a high likelyhood that it's already been fried since this is a very common problem with these cars) I had a TV repair shop in the area swap the chips for me for $100 once I obtained a junkyard computer. But if you have time to wait for shipping, you can get the STA508A chip in the mail really cheap. It'll save you lots of money and hassle, but waste lots of time unless they'll overnight it, which negates some of your savings.

3. Put a 7.5A fuse in the ENG CONT1 slot in your fuse box found beside the battery next to the firewall. This is an important step because it guards the computer against getting fried again. The 7.5A fuse replaces the 15A fuse that allows too much current to go through and fry the computer.

4. MAKE SURE YOU DON'T TURN THE CAR ONE BEFORE YOU'VE DONE ALL OF THESE STEPS AT THE SAME TIME. Not doing any one of these steps can potentially kill one of your brand new components immediately. So be careful and thorough when you follow these steps.

After that's done, you can attempt an idle relearn, but idle relearn only works if everything is running normal (meaning all the voltages in the system are normal and everything's running fine so it doesn't throw off the idle relearn). If something's still messed up in the system, the idle relearn won't work, if I understand it correctly.

I'm new to Maximas, so if part of my explanation above is incorrect, one of the experienced members will correct me.

After you do this, you'll have a lot more peace of mind. I sure did. I love fixing things on my car and preventing them from happening again, especially since I drive my car a ton every day for work. You'll be glad you did all of this once it's done.

Even if you suspect this isn't your car's current problem, I'd do it anyway because generally, Maximas eventually have this problem and it's a pain in the ***.

Good luck, man!


- Brian

jcd2

Well after trying an unsuccessful IACV re-learn several times back in January I disconnected the battery and finally got some decent dry weather yesterday. I checked the throttle plate to make sure it was fully closed, changed the PCV valve, checked tension of the throttle cables and made sure no air leaks down stream (towards air box) were present. Today I drive the car for about fifteen minutes with high idle to satisfy all pre conditions were satisfied. Tried doing the manual re-learn twice and all I got was the erratic idle back (bouncing between 1590-2 RPM'S. I called the nearest Nissan stealerships with a service department and the guy didn't know what a consult II was or whether the service center had one. The giy also didn't understand what the Idle Air Control Valve re-learn was. Told me to call back at a different date and hopefully their Nissan advisor would be there to understand and help in a better way. So.... what can I try next? I'm leaning towards replacing the TPS sensor????

Cephyr13

Just look at my post right above your last post. It tells you what the problem is, most likely, and how to fix it. It's a very common problem with these cars, so much so that it puts them in the junkyard a lot. So it's best to fix it now before your car kills over. And even if it's not the problem with your car, it's something every Maxima owner should do because it's likely to happen anyway and could disable the car completely when it happens. I can almost guarantee if you follow my instructions in my last post, it will fix your problem. It's exactly the same problem I had. It sounds like a lot and like a hassle, but it's really not bad once you start doing it. You can do it all yourself excerpt soldering the transistor on the board. Don't let that scare you. Just take it to a local TV repair shop.

I can also almost guarantee that if you don't follow my instructions above, you will never solve this problem. In which case, I'd like to buy your car for $500.

Doing this fix to a Maxima is a no-brainer man. Trust me. But follow the instructions to a T so you don't kill parts unnecessarily. Good luck.

jcd2

I appreciate the reply sir. I plan on doing all the above once I get yhe initial idle fixed. I had already had the computer fixed and replaced the IACV.the two times it's ran, I haven't gotten the P0505 code.

mcdudeman

I have an 01 SE MT that I recently purchased for $300 and it has an IAC issue as well. When I was at the junkyard to get a strut someone told me my IAC was bad (which I already knew) but also said that my ECM was also gonna be fried (which I did not know happens). I would like to know, what actually gets fried in the ECM and what does it do exactly? I mean the car runs great otherwise, everything works on it without issue (minus foglights and ABS). The only upside I can see to fixing it is less fuel consumption at idle, and it wont sound as obnoxious when I am idling (someone removed the resonator so it sounds very loud... but so far having a loud car that idles like vroom..vroom..vroooom..vroom.. has actually made it easier when I need to pick someone up, I simply tell them to listen for me).

I do not know how long it has had this issue, but the car runs like a dream, getting ~32MPG on the highway and still having the power to reach 138MPH (have not been able to go faster as I end up running out of room or traffic appears).

So........... TLDR: My 01 idles erratically, I was told it was a bad IAC and ECM. It really doesn't bother me just those around me (resonator was removed). It does idle high (like it should) when it is cold until it warms up and during that time it keeps a constant 2500 (i think) RPM. My question is, will my car die if I do not fix the IAC?

*Forgot to mention, the car does not give any codes about the IAC. Only an occasional random emission code (passed emissions just fine), a neutral safety switch code (seems to happen when using cruise control), but thats about it. I have a Garmin Ecoroute HD that connects my GPS to the OBDII port and I can actually clear the codes while im driving when they appear.

Cephyr13

Oh, I see the misunderstanding now.

It's pretty much impossible to fix the idle while this problem is occurring. The problem with the computer and IACV is the cause of the idle issue you're having. My idle was never correct on my car until I fixed both the IACV and computer at the same time like I laid out above. I tried what you're trying and nothing would correct the idle. I don't have time to explain why this problem causes the high idle.

I did not have the p0505 code to indicate the problem, so that code doesn't have to show up for you to know it's the IACV-ECU problem. I can almost guarantee if you'll follow the instructions I first posted, when you're done, your idle will finally be correct. What you're experiencing is basically the same thing I experienced with my Maxima.

- Brian

maxiiiboy

jcd2: Read the document about ECU failures (link is in my signature) and make sure you understand all the issues before replacing any more parts.

maximatech12

they most likely don't use these because the team techs have their own computers fully equipped with Nissan Reprogramming software.
keep in mind these techs see dozens of different models per week!

They do have Nissan Data Scan II available for download online. This will give you the opportunity to reset "target idle speed" yourself as well as monitor all the voltage.
also you can program blank ECU's and sub keys