Engine Quit with Electrical Burning Smell

[pstarbard]

Hi All,

I have a 2001 Pathfinder w/ ~190K mile on it. It has been used regularly until this past winter. It has been sitting for about 3.5 months and I'm just now getting it back on the road. The battery has been draining due to non-use but I charge it and the car will start. Today I started it and after running for about 2 minutes the engine quit. When I got in the car I noticed the strong smell of electrical burning but no smoke. I did not notice this outside of the car. Upon trying to restart the car the engine just cranks with no sign of trying to start (as if there's no spark). I suspect something (probably electrical) has failed while it was idling but I have no idea what it could be. Any ideas and or help would be appreciated.

Thank you.

[4xq]

There is a known problem on these vehicles that has appeared as they age. The Idle Air Control Valve (IACV) gets a short in it, and sends too much voltage to the Engine Computer Module. A MOSFET in the ECU dies when that happens.

You can remove the ECM from under the dash (to the drivers side of the console). It is now way out of warranty, so there is no reason not to remove the screws and take the case off. You should see a bad MOSFET ( it stcks up from the circuit board).

To fix, you need to replace the IACV with a new one, and get the ECM fixed. Look on EBAY - there are several places that advertise that service. Runs 85 to 200 dollars.

If you actually replace the ECM with a new / used one, you must have your keys programmed to the new unit. That is not necessary of course if you have yours repaired.

I think that is most likely your problem. Let us know!

[pstarbard]

Thanks for the detailed info. Seems to make sense given the symptoms. I'd like to confirm this is my problem before I spend the money on a new IACV and the repair of the ECM. Any suggestions on how I can go about that? Specifically, how can I verify that the IACV has a short and how can I verify that the ECM is bad? For the latter, you mention a bad MOSFET. How can I tell a bad one from a good one?

Thanks,
Al

[4xq]

There are no detailed specs on the IACV that I have seen. However, the service manuals are here: http://www.nicoclub.com/FSM/Pathfinder/ ... athfinder/

Go to page EC-420 where the wiring diagram for the IACV is detailed. Pins 2 and 5 supply voltage, so they should be 12v. Measure the ohms resiatance off to the other four pins from 2 and 5. One or two of them should show some kind of problem, as in zero or very low resistance compared to the others.

The MOSFET is a flat wafer type component that sticks up from the circuit board. It will probably have visible damage to the side of the wafer.

The no start condition and electrical smell are pretty strong evidence that is what happened. Hope that helps!

[pstarbard]

Thanks. I'll check it out.

Al

[pstarbard]

So far, so good. I've removed the IACV and the ECM. Upon inspection, the ECM MOSFET was visibly fried, like you said. I'm ordering the repair and the site says that the IACV AND the throttle position sensor need to be replaced at the same time as the ECM repair. You mentioned the IACV and I've ordered that but, is it necessary to also replace the throttle position sensor? Are they saying both need to be replaced b/c it could be either that went bad and damaged the ECM (and they don't know which)? Everything I've seen thus far says the IACV must be replaced but this is the first mention of the throttle position sensor that I've seen. The site I'm looking at is http://www.ebay.com/itm/01-02-03-NISSAN ... #vi-ilComp

Thanks,
Al

[4xq]

Well, I have heard that being reqiured by a couple of the repair shops, but have not really seen it as a problem in the Pathfinders - I kind of think it is a generic requirement that they have which is based on repairs they have done to many diffrent types of ECM's. So, if you have a problem and want them to honor their warranty, you will have to produce a receipt showing you bought a new one.

You can find enough info in the service manual to test yours - you want to see it go from 0 volts to about 12 volts smoothly as you move the throttle from idle to full open position.

If you read the service manual you will see a lot of inputs that depend on the TPS - its kind of amazing how central it is to everything.

[pstarbard]

Ok, I received and installed both the new IACV and repaired ECM. All the installation was done with the battery disconnected. I then reconnected the battery and attempted to start it but it just cranks. There is no burning smell like last time, so I don't think I fried the ECM again. There is a slight smell of gasoline once I stop cranking.

Can you think of anything else I need to do before it will start with the new parts? Is there anything I should check?

Thanks,
Al

[4xq]

Just check your fuses - probably took one out when the ECM went. Check ELEC B fuse and any other fuse under the dash labeled for ignition or engine.

There is also a fuse box under the hood to check if fixing fuses under the dash doesn't get you running.

[pstarbard]

That was it. 10A ECCS2 fuse in the box under the hood was blown. Replaced it and it started!

I'm back up and running again. Thanks for all your help. It's much appreciated.

Al

[4xq]

Glad to hear it worked!

[2001PathfinderLE]

Same thing for my 2001 Pathy. Had the ECM repaired by an eBay vendor and it still won't crank. Checking the fuses tonight, fingers crossed!

[2001PathfinderLE]

Update, it was indeed the fuse, thanks to this forum for the fix! I'll read all the posts regarding the ECM and blowing fuses next. As I mentioned I got my ECM repaired from an eBay vendor and when it didn't crank I sent it back to them. They tested it again and stated it must be something else.

Gotta love Nico for coming to the rescue.

[4xq]

Lot cheaper than taking it to the shop!

[pstarbard]

The saga continues... So, it was running fine for about 3 months, then esterday afternoon while driving slowish through a residential neighborhood the engine stalled when I took my foot off the gas. Tried to restart and found that the engine won't run at idle but will stay running if I give it a little gas. I'm guessing this could be related to the IACV problem. But the IACV is new. Any ideas? Could it be something else?

Al

[Buzzman]

Unfortunately, that symptom is exactly what you get when the IACV dies.
Where did you source your new IACV?
I would also be cautious about driving it too much like that. The ECM could go again.
Are you getting any codes?

[pstarbard]

I got it from Parts Geek. I haven't checked the codes yet, but I will. Strangely, it started working fine again today.

[EdBwoy]

I'm hoping it isn't the throttle position sensor this time.
Although like most electronics the iacv could've just randomly quit. Did you by any chance do the idle relearn procedure when you replaced that iacv the first time?
Sometimes vehicles "forget" the idle settings. I'd try the relearn. It's free anyway

[pstarbard]

Didn't do the relearn. Everything seemed to be working fine so I didn't think I needed to. I'll look that up and give it a shot. Thanks.

[4xq]

Post the codes if you can - 505 code is kind of the IACV code for this problem.
Doing the relearn is a good idea as well.

[rgk]

I second pulling the codes. Although the symptom is the same, it could be an issue unrelated to the IACV.

However, the symptom does point to it, which is frustrating. Here's what I think:

The TPS will likely cause shifting issues, but I haven't heard of it causing the car to stall. You can try unplugging it to see how the car runs.

Is the IACV OEM? Was it purchased new, used, or remanufactured? I doubt a new IACV would cause this problem three months down the line. The only "new" part that I ever had trouble with a few months down the road was a remanufactured starter, and I've purchased a lot of car parts. Even cheap Chinese parts last for at least a year, in my experience.

Speaking of remanufacturing, the part I would be looking at is the ECM. Seeing as how it was fried and refurbished, I would assume this to be your weak link. Is it possible for you to track down a cheap used unit for testing? Or perhaps send it back to your ECM doctor for diagnosis? Maybe you can just remove it and examine it yourself.

I agree that pulling the codes is your top priority. However, if I remember correctly, the idle relearn procedure is only relevant to 2003 and newer vehicles, as they were equipped without the typical cable throttle. Someone please correct me if I'm wrong.

Good luck and, as always, please keep us updated. :+)

[atraudes]

When my TPS died, the engine idled high (1500 rpm) and shifted really hard. A TPS on the way out would result in erratic or unusual engine behavior, but it wouldn't affect the idle in this way.

It's entirely possible you got a defective unit, but I'm surprised it waited as long as it did to die (assuming that's the case). For me premature deaths tended to come in the first few days of use. I'm currently on my 3rd fuel damper and have the 4th on order. All 3 were DOA.

What brand IACV did you buy?

[Buzzman]

I agree that pulling the codes is your top priority. However, if I remember correctly, the idle relearn procedure is only relevant to 2003 and newer vehicles, as they were equipped without the typical cable throttle. Someone please correct me if I'm wrong.

Good luck and, as always, please keep us updated. :+)

The relearn is relevant from 2001 and on (3.5 engine).
Mine is a 2002 with the mechanical throttle cable, and it required a relearn after I replaced the IACV and the rebuilt ECM.

Not sure about the 3.3 engines though (pre 2001). I thought I saw somewhere on here that they don't have a relearn procedure.
Cheers.

[pstarbard]

Seems to have taken a turn for the worse. I tried to read the OBD codes but my reader wouldn't work so took it to auto zone and they couldn't read it either. There are a few other anomalies as well: the clock has stopped working; the remote lock/unlock has stopped working; the A/C is not on when I start it even though it was on when I shut the ignition of the previous time I drove it (and it resets to 75 degrees even though I had left it at 68). Also, I've figured out how to make the idle problem go away (have someone start it while I hold the throttle open). This has worked for times but the problem returned after a few days each time.

Does all this mean the computer is shot again? Is there a way to reset it or troubleshoot it?

Thanks,
Al

[rgk]

You can always check resistances, voltages, etc., from various circuits to the ECU, but think about it: what else would cause all of these weird problems?

I would be contacting the place you had the ECU "fixed" and let them know all of this is happening. It most definitely sounds like an ECU issue. Hurry, though. Warranties don't last forever.

[4xq]

Your ELEC B fuse popped - it is a 7.5 amp fuse. That should fix the OBD port and the remote entry if I recall correctly - not sure about the other stuff.

Start there first!

[pstarbard]

It was the fuse. Replaced it and the remote entry, click and A/C problems were fixed. Haven't tried the OBD yet but will do that tomorrow.

[pstarbard]

It was the fuse. Replaced it and the remote entry, click and A/C problems were fixed. Haven't tried the OBD yet but will do that tomorrow.

[pstarbard]

So, I tried the re-learn procedure and it didn't fix the problem. The engine still won't idle unless I give it a little accelerator to keep the RPMs at 500 or better. I checked the codes and found the following:

P0505 - Idle Air Control System
Probable Cause: Large vacuum leak, engine mechanical condition or failed IAC valve.

P0455 - EVAP control system gross leak detected (I've had this code for more than a year, way before the IACV and ECM problem that started this thread, and it comes back after being reset)
Probable Cause: Faulty fuel cap (got a new one and problem didn't go away), purge system leak, faulty canister vent control valve or faulty purge control valve.

P1448 - EVAP canister vent control valve (open)
Probable Cause: Failed canister vent solenoid or failed EVAP pressure sensor.

P1140 - Intake valve timing control position sensor (left bank)
Probable Cause: Open or short circuit condition, poor electrical connection, failed intake valve timing control position sensor.

P1110 - Intake valve timing control (left bank)
Probable Cause: Open or short circuit condition, intake valve timing control position sensor fault or blocked signal due to debris.

Based on this, I could replace any/all of the following parts:
- canister vent control valve
- purge control valve
- canister vent solenoid
- EVAP pressure sensor
- intake valve timing control position sensor
- idle air control valve (already replaced this once)

Any ideas on how to narrow down the failed part? I suspect it's one part and all the other codes are cascading from that.

Thanks,
Al

[fastpakr]

Just a shot in the dark - have you tried probing the MAF output with a meter? I had a similar issue a couple of weeks ago where it would stall when warm. Turned out the MAF was never coming above the baseline idle reading of .9v. Swapped it with a Maxima unit and everything went away. That said, mine did throw a MAF code (P0100 IIRC) and it sounds like yours isn't.