How do you reset the ECM on a 1998 Pathfinder?

[r0x]

I would like to do a "hard reset" of the Engine Control Module (ECM) on my 1998 Pathfinder 3.3 V6 in order to force it to purge old data and return to factory defaults. How do you do that? Is it sufficient to disconnect the battery for 15 minutes or is there more to it than that? Thanks, r0x.

Edited April 22, 2008 by r0x

[nissandoms47]

Unplug the battery overnight.

[XPLORx4]

It doesn't need to be overnight. Disconnecting the battery long enough for the radio to lose its presets is usually sufficient to reset the PCM, too. 15 minutes is more than adequate.

 

Why do you want to reset the PCM to "factory defaults"? Short-term and long-term fuel trim settings get re-learned as soon as you start driving again, and they're constantly adjusted anyway.

Edited April 23, 2008 by XPLORx4

[r0x]

It doesn't need to be overnight. Disconnecting the battery long enough for the radio to lose its presets is usually sufficient to reset the PCM, too. 15 minutes is more than adequate.

 

Why do you want to reset the PCM to "factory defaults"? Short-term and long-term fuel trim settings get re-learned as soon as you start driving again, and they're constantly adjusted anyway.

 

I needed to have the distributor assembly replaced and now I'm getting SES with DTC P0505 (IACV-AAC Valve does not operate properly). I did not have this problem before the ignition system failure. I thought that perhaps the ECM somehow got into a weird state and that resetting would force it to relearn, among other things, the idle control valve operation and clear the problem. As it turned out this did not work...

 

The truck idles high when I first start it up at about 1500 RPM at Neutral and about 1200~1300 RPM in Drive. This is probably what's triggering the error code. Once the truck has warmed up idle goes down to about 1000 RPM at Neutral and about 750~800 RPM in Drive.

 

The moderator on NissanHelp.com suggested that the symptoms and DTC P0505 is due to incorrect timing setting with the new distributor rather than a problem with the idle control valve. I haven't been able to get a hold of the repair technician to follow up on that.

 

Another possibility is that the idle control valve really is bad, which would really suck because the freakin' thing is on the back of the engine facing the firewall. My local Nissan dealer wants $200 for a new valve and $550 for labor, which is why I posted a question about the "ghetto idle control valve cleaning method" on another thread:

 

I found these "urban" IAVC-AAC cleaning instructions on another forum:

 

http://forums.nicoclub.com/zerothread?id=251133

 

 

QUOTE

Ghetto way to clean iavc is.

step 1. start car

step 2. while having a friend rev engine, partially remove the 2ND (bigger of the 2 hoses) right beside eachother on your intake(stock - going from engine to airbox)

step 3. if you have managed to keep car running while pulling it PARTIALLY OFF then continue if not restart

step 4. spray a **** load of throttle body cleaner in there and reatach hose while keeping engine running.

repeat as needed

 

 

I am toying with the idea of trying this because the idle control valve is virtually impossible to get to on a Pathfinder without taking half of the engine apart. Any comments appreciated.

[nissandoms47]

When I unplug my battery it resets my radio presets instantly.. I know my pathfinder i would have to keep the battery unplugged for another 20-30 minutes for it to reset the ecu. My xterra takes a very long time. Long enough to where i just use my code reader to reset it. You might just need to adjust the idle screw on the TB or maybe the IACV valve has been unplugged.

[XPLORx4]

Before you do anything to the IACV yourself, you should take it back to the mechanic who did the work. It is unlikely a mere coincidence that this error code appeared immediately after having repairs done. Incorrect timing can influence engine speed. I wouldn't try randomly adjusting stuff yourself; you might make things worse.

Edited April 24, 2008 by XPLORx4

[r0x]

Before you do anything to the IACV yourself, you should take it back to the mechanic who did the work. It is unlikely a mere coincidence that this error code appeared immediately after having repairs done. Incorrect timing can influence engine speed. I wouldn't try randomly adjusting stuff yourself; you might make things worse.

 

I took it back to the place... Twice!

 

The first time the tech just verified operation of the idle control valve with his MODIS. I watched as he adjusted the signal going to the IACV and the corresponding changes in the idle speed. He then asked me to go out and buy a bottle of NOS-brand octane booster and add it to a tank of premium gas. The old truck runs great on this good stuff but the idle speed was still to high when all was said and done so the computer threw out a DTC P0505 again within 1/2 an hour of leaving the shop.

 

This morning they re-verified the timing, cleaned out the throttle body, "ghetto blasted" the IACV-AAC (see previous post for an explanation), and adjusted the neutral idle speed to about 900 RPM. (He didn't want to go any lower because the truck idles at 750 RPM in gear. I have no idea how he was able to reach the idle adjust screw.) All is good for now - so far no DTC P0505.

 

Hopefully this is the end of the story. Thanks to all for advice and replies.