EuroDriver

iTrader: (21)

I'm taking my '01 in for an ECU reprogramming to the stealership tomorrow morning. I scheduled the service for ECU Reprogram & Idle Air Relearn.

Question is, does the ECU reprogram necessarily include the Idle Air Relearn? Just want to know in case they want to charge me separately, whether I should only be charged for the reprogramming.

I have been battling with a high idle problem (1000 - 1100 RPM in Park/Neutral) - mostly when warm, and surging between 1500 - 2000 RPM. It includes a persistent P0505 code. I replaced the IACV & MAF, numerous battery disconnects & manual idle air relearns to no avail. I have found a number of threads on this issue, but none offer a cause or fix. As such, my wrench recommended having the ECU "reflashed" so being out of options, off I go.

Any info on any/all of the above greatly appreciated.

tech44

Hi Euro Driver,

I'm starting to get hesitant to chime my thoughts in as a dealership technician, but I'm going to go out on a limb here and hope you're more appreciative of my help. Typically, an Idle Air Volume Relearn is separate from a reprogram. Nissan's warranty times and bulletins outline if it is included or extra. As far as the procedure goes, performing them is 2 separate operations. When a reprogram is done, it doesn't automatically adjust the IAV; so the relearn is done afterwards. They may or may not charge you for the relearn; that is up to the service department's discretion. Nissan/Infiniti vehicles around the model years of your vehicle definitely do require it after reprogramming, as it may return with a service engine soon light related to idle speed control. When ECMs are replaced, typically the part has the most up to date software available. I have had general automotive shops replace ECMs and request an update only find that it already has the most current software; I 'no charge' those as there was no real work performed.
May I ask what their labor rate to do it is? I'm just wondering as there is a universal labor guide by Mitchell that contains the times in which the jobs should be done.
I am also wondering if you've recently replaced the ECM. The idle speed control motor circuit has no fuse protection so if the idle speed control motor shorts from coolant, or just draws too many amps, it will damage the ECM.
Anyways, stuff to think about. I'll keep my eyes on the forum and see if you've got any updates I can hear about.
The 2002-02 models have the motor throttle actuator so they do not see this problem. The 2000-01 models are where I will see this issue.
Thanks.

EuroDriver

iTrader: (21)

First of all, I most definitely appreciate your thought/opinions, especially as a service technician, I'm hoping you may have a little more insight or experience with this problem.

To first answer your questions though, I have not replaced the ECM. Dealership would not quote me a price on ECU reprogram- only told me diagnostics start at $49.00. My mechanic told me the dealership would charge me $139.00 to do the "reflash" (and told me to ask for a certain technician in particular & tell him he sent me).

My mechanic thinks my car threw the P0505 code after I did some unusually spirited driving in a 1-hour road trip because I threw the ECU for a loop from its learned values, and that I probably unnecessarily changed out the IACV as a result of it, an 7d that the code got stuck in the ECU, which in order to avoid unnecessary trips & headaches, suggested a reflash by a Nissan dealer. He seriously doubts I damaged the ECU- says I'd be having much worse problems if I had.

My issues started after a road trip on which I drove the car unusually hard (at least for what I have it used to). P0505 came up after about an hour (when I was almost home). I cleared the code and it remained off for a couple of days until my brother attempted to do an idle-air relearn on it. The instant he unplugged the TPS, the light came on again and has been pretty persistent. I was having these issues:

- my idle would be a little high after the car is at full operating temperature (1000 - 1100 RPM; it had done it occasionally in the past, but kind of seldom, so I never gave it much thought).

- Also, the transmission seemed to occasionally have displaced shift points (delayed O/D on hard acceleration & delayed shifts - especially from 3rd to 4th).

After reading up on P0505, I decided to replace the IACV this weekend (for fear of frying the ECU). First though, I cleaned the old one and ran the car for 10 mins. At first it started fine and drove fine. When I got back home though, Idle was high again & SES came back on.

I proceeded to replace the IACV (with one from AutoZone). After running the car about 30 minutes, high idle & SES again. I could clear the SES light, but scanner kept picking up the code - SES came back on a few more times. My brother then attempted to adjust the TPS. When that didn't work, he tried to put it back to its original position, but idle shot way up & couldn't be adjusted.

Next day, I take it to my mechanic. After adjusting TPS properly, idle remained very high & was surging. He controlled the IACV with the Consult II, but as soon as he'd exit the program, high idle & surging would resume. He determined the new IACV was defective & sent me to the dealership for a new one. After install, car ran stable, except for:

- idle remains high (1000 - 1100 RPM)
- engine surges at range of 1500-2000 RPM
- P0505 keeps getting triggered
- acceleration feels slightly sluggish to me (feels as if I had a couple more people in the car)

I have tried numerous times to disconnect the battery (10 mins, 1 hr, 2 hrs), and doing the idle re-learn, but neither has produced a change.

One of the things that has me worried is that my mechanic's Consult II (I'm assuming that's what it is - it's a huge, 2-hand-held-scanner-looking-apparatus by Snap-On) gives him the option for Air Idle Relearn, but when he hits OK to start test, nothing happens. He thinks that although the option is there, the tool does not have the software to carry it out. I'm getting concerned it's an ECU malfunction.

Any experience with this type of issue? What's your hunch?

tech44

Hi Euro Driver,

Thanks for the quick reply. This is a tough call. A code that does not clear, to me means that it is a hard fault and is something current. The nice thing about that is that you know it's not intermittent and you can go about your testing. here's why I think it's a tough call. I'd hate for you to have to go to the dealer to program an ECM and find out it is burnt out. If you want, you can remove the ECM and remove the cover; look for a burnt chip. You may also notice a burning smell. It's not really easy to get out, but it is do-able. I believe it is located behind the center console on the floor near the firewall.

EuroDriver

iTrader: (21)

I forgot to include is the following:

When the car is cold, it will idle at about 850-950 rpm's. Once it warms up, it goes up about 100 rpm's.

Also, my mechanic tested the new iacv, tps & maf. He showed me they're all working perfectly.

I have been avoiding pulling the ECU like the plague. However, I have stuck my nose pretty far down there and don't smell anything unusual. That, coupled with my mechanic's opinion that a bad ECU would lead to much worse symptoms maybe has me wanting to convince myself it's not the ECU. I guess I'll roll up my sleeves & get it done tonight before I go spend my money tomorrow.

EuroDriver

iTrader: (21)

Just pulled the ECU. It's intact, THANK GOD!

noahrexion

So you did in fact check (resistance) the IACV properly?

Since you have an old OEM unit and new Autobone unit - you might as well try the same testing procedure(s) on each one. This may tell you a lot - in the way that maybe the new IACV is (still) the problem (although the 505 does indicate this). You may need to buy an OEM IACV.

If that is the case, you might also consider bypassing it (from coolant) all together so that you know you won't have any shorting issues in the future with the new unit.

Thanks for keeping current on this, I always appreciate when posters follow up with progress/solutions.

EuroDriver

iTrader: (21)

I returned the AutoZone iacv and purchased another one at the dealership. Made a huge difference from the autobone one but still runs like with my stock one. My ohmmeter wouldn't duplicate values so I gave up on testing.

DaveD

Been thru this, but when my iacv was bad, it would start but not idle. It would just stall almost immediately, you had to have your foot on the gas pedal to keep it running until it warmed up. There is something called a stepper motor on the iacv. After it was all said and done I took it off of the old iacv and cut it open and it smelled like antifreeze without doubt. Anyway I'm not sure if your saying that your car is fixed or not? If not I'll try to post the idle relearn procedure that worked for me.

EuroDriver

iTrader: (21)

I replaced my IACV with an OEM and still had high idle, but no stalling. The other quirk is a surging problem that only occurs between 1500 to 2000 RPMs.

This morning I had the intake manifold gaskets replaced, just to rule out the possibility of a vacuum leak. So as we speak, my car is at a local dealership having the idle relearn reprogrammed.

However, it would be nice if you share your relearn procedure for reference. I tried the method specified in the FSM countless times with no luck.

DaveD

Sorry, I just typed all that info. in there and when I submitted it it said I need to log in which I was. It's like it times you out

DaveD

For what it's worth, I think you have a vacuum leak which can come from many places other than the intake gasket. I would rule out the iacv if it were me.

EuroDriver

iTrader: (21)

That was my mechanic's hunch, so he took out the intake, went through all the vacuum hoses very carefully - all said and done, nothing changed. Per other folks I've gotten feeback from, their experience has been that sometimes a reprogramming is required. I'll find out soon enough.

EuroDriver

iTrader: (21)

Just got a call from the dealer - they are keeping the car overnight.

According to the rep, they can't get the programming done because the car keeps triggering the P0505 code and the fans come on while they are attempting it, so they want to try it in the morning after it has cooled overnight. So one more night of suspense, lol!

EuroDriver

iTrader: (21)

Nissan just called, said the computer is not receiving signal. $1200 to change it.

Here's the twist: They're not sure the computer really is the problem - they said it can be a bad harness or wire somewhere. About $550 to do a full diagnostic to really find out for sure, so leaving the call up to me whether to invest in diagnostic or ECU...

I checked the ECU - there's no burnt chips in it.

EuroDriver

iTrader: (21)

Here's some pics of my ECU:







Looks fine to me - there was no unusual odor to it. Can s chip still be bad & not show it?

My cheapest options seem to be:
1) spend an enormous amount of time testing harnesses and chips; or
2) find a used ECU, pay to have it reprogrammed & see if it fixes the problem.

cjandura

iTrader: (3)

I vote #2 contact Aackshun for a ecu also whats not communication just the odbII port? if so whip out the fsm and check the connections.

noahrexion

For your sake you should really just swap ECU's with someone that has the same type of whip to rule it out (or in) before spending any money.

Your car drives, albeit annoyingly so, so why not wait on it till you know.

Definitely don't pay the dealer any $$$.

EuroDriver

iTrader: (21)

Today I replaced both temperature sensors with new, oem ones. No change. Last stab in the dark will be the power steering pressure switch, which will be arriving Wednesday. If that doesn't fix it, it will be time for drastic measures. I guess ECU swap would be the next move...

EuroDriver

iTrader: (21)

I think the OBDII port is ok - they were able to test the IACV, TPS & MAF and determine they're functioning fine. What's not communicating is the test instructions for the IACV relearn.

EuroDriver

iTrader: (21)

Been a long day - testing sensors, switches, wiring, ecm. Many test drives in between. However, looks like it finally yielded results:

Auxiliary Air Control Valve (power steering). Hence, why FSM refers to IACV/AACV. (see, FSM, EC-429 et. seq., especially p. 434).

I checked it at the hose to the airbox and there's no vacuum at all. Hopefully, I find one in stock tomorrow to confirm.

EuroDriver

iTrader: (21)

I misdiagnosed the power steering air control valve. I ended up taking the car to another shop who reportedly adjusted the idle screw in the throttle body and readjusted the TPS. When I got it back, the idle was still at about 900 RPMs. Drove it around all day and the P0505 code did not pop back up. This morning I attempted the idle relearn again and BAM - IT TOOK!

So the idle is now at perfect target speed, but my last remining issue is an idle surge between 1500 - 2000 RPMs. For one, I suspect the shop merely cranked down the TPS to attempt to control the idle. (I called them this morning to inquire about the surging and the TPS settings they adjusted - they told me to "just keep driving the car and it should readjust," lol!). I'm going to re-check the TPS settings this weekend, and the surging is not causing the P0505, so I'm just going to start a new thread for that one.

Hope this helps those of you with this dreaded problem...

Maxatnite

Just talked to a guy at Avpro and apparently they have developed a module to replace the STA509A for the idle speed and the STA508A for the active motor mounts. He said they are still testing it. It detects overload and shuts down all drive to the idle valve for 2 seconds preventing damage. He said the will be selling it separate from the repair they do. I may replace mine before I have a P505 code. The ecu will still throw the code if the iacv goes bad.