IACV Relearn Procedure Tips (P0505, idling issues) using a phone app

[vancouverpathy]

Hey,

Long time reader and find this forum to be a vast resource for maintaining my Pathy so thought i'd share something I learned today whilst doing the IACV relearn:

Backstory: I had to replace ignition coil #4 which required removing the IACV solenoid. After putting everything back together my Pathy had forgotten how to idle properly. I've read several posts here where people have encountered issues performing the idle relearn (with consult-II and without) and have encountered inconsistent results myself, until I figured out why.

I'm using the "NDSII" app on the android app store (you can do an idle relearn with the free version).
Follow the procedure laid out in the FSM: EC-58:

"PRE-CONDITIONING
Before performing “Idle Air Volume Learning”, make sure that all of the following conditions are satisfied.
Learning will be cancelled if any of the following conditions are missed for even a moment.
- Battery voltage: More than 12.9V (At idle)
- Engine coolant temperature: 70 - 99°C (158 - 210°F)
- PNP switch: ON
- Electric load switch: OFF
(Air conditioner, headlamp, rear window defogger)"

*also make sure no SES codes are present; clear them if they are emissions or IACV related (P0505, etc.).
Anything more serious that trips SES early on engine start will need to be addressed before this procedure will take

OPERATION PROCEDURE With CONSULT-II (2001 - Pathfinder)

• 0. Ensure your phone and the OBD-II dongle are paired before proceeding.
• 1. Turn ignition switch “ON” and wait at least 1 second.
• 2. Turn ignition switch “OFF” and wait at least 10 seconds.
• 3. Start engine, warm it up to normal operating temperature and check that all items listed under the topic “PRE-CONDITION-ING” (previously mentioned) are in good order. If you're already at temperature you don't need to keep the engine running very long at all; ~10-15 seconds)
  
  This is the critical part (keep good timing):
• 5. Turn ignition switch “OFF” and wait at least 10 seconds.
• 6. Start the engine and let it idle for at least 30 seconds:
  During the 30 second idle connect your OBD-II dongle/cable to your phone and fire up NDSII.
  Tap Connect and select your OBD-II dongle from the list and wait for the app to register with the vehicle.
  
• 7. Scroll screens to the “WORK SUPPORT” page of the app and tap “IDLE AIR VOL LEARN”.
  The second you start the idle learn the ECU will drop the RPM *slightly*.
  If the RPM doesn't get at, near or below 750 RPM the idle learn will go on forever.
  I've found that if the ECU won't drop the RPMs enough, the procedure will keep failing and throw a P0505 when you cancel.
  If the RPM looks too high after initiating the procedure (mine was ~900), use the top of your foot to pull up the accelerator pedal to reduce tension on the throttle cable and lower the RPM manually to around 750.
• 8. Touch “START” and wait 20 ~ seconds (The app will tell you pretty quick if the relearn took; FSM says 20 seconds but mine only took ~5)
• 9. Rev up the engine two or three times. Make sure that idle speed and ignition timing are within specifications.

If you follow the procedure to the book, and ensure that just after you initiate the IACV relearn that the RPM gets to 750 (by the ECU, accelerator pedal or loosening the throttle cable if necessary), the relearn will stick.

Anyways, hope this helps some frustrated pathy owner trying to teach their wagon how to breath properly at a stop light.

Thanks for all your help on here.

Cheers,
B

[AlanAZ]

Good information, thank you for posting.

One suggestion. Before doing a re-learn, perform a ECU reset by disconnecting the battery for overnight (10 minutes won't cut.) This alone may correct the problem, but if not, will give you a blank ECU (all learning and codes wiped) to work with.

[EdBwoy]

Welcome to the forum... and thank you for sharing this.
I will add this to the FAQ section