My parents 2002 pathfinder 3.5 v6 auto 4x4
Problems started after my dad replaced a dead battery car ran great before, sudden problem. Realising now that may have caused the car to forget throttle.. The car suddenly died while driving twice but would restart and drive normally. Then some idling issues, they took it to a mechanic who "cleaned" the throttle body he said if that diddnt do it then replace the tb lol. the car was throwing p0159 and p1167 (02 sensor slow response and max volt monitoring.) After back from mechanic the car would idle sporadically up and down, changing when in gear.
I noticed right away the iacv was leaking pretty bad onto a coil, whole area was soaked. Must have been a lot of coolant getting into the throttle body. I replaced the iacv right away then after some research realized it can fry the ecu one will short out the other when bad.. cleaned the throttle body properly and replaced gasket. Back side of tb was quite dirty.
After starting and running nice for a few moments the idle dropped then died, wouldn't start without manually giving it throttle. Pulled a code for low idle, after waiting for my new pos scanner. It only picked up the max voltage 02 code.cleared codes. Tried various throttle relearn procedures and nothing seems to stick. Tried what's in the manual at page ec-72 and after trying multiple times I found this page https://www.altimaforums.net/threads/id ... -way.3398/ wich helped. Got the check engine light to start blinking finally as one of the last steps but it is supposed to stay steady illuminated after 20s. Just kept blinking. The idle would seem to learn for one start up then forget for the next, or if I revved engine a few times it would drop to 250-400 rpm stutter or die.
Took for a couple test drives diddnt help though runs ok while driving after pedal position realearn just too low idle trys to die at a stop. Cel still off.
I want to test and replace pcv and plugs but have to remove tb and intake manifold wtf?! I want to tune it up. Going to clean maf tomorrow and see if it helps.

Would it fail to learn if the maf was bad or 02 sensor was bad? Time to check ecu for fried chip? Could the ecu be fried at this point? It runs great right after learning throttle then forgets..
Was hoping not to replace the 02 sensors but noticed today one was covered in oil.. oil leak seems to be coming from oil cooler and running all the way down almost looks like leaky tranny and maybe axle seal too goodness.. Going to dig deeper soon any help much appreciated! Trying to save them some money but this is getting more and more complicated and they need the vehicle soon.

The car won't forget throttle position when the battery dies, but the mechanic may have moved the throttle position switch when cleaning the body. Yes, it's entirely possible that the coolant fried the ECU. However, before you go that route, try the following first.

First, make sure your throttle position switch is in the right position. Start with the FSM on EC-117 and follow it to the letter. Start with steps 1-4, skip steps 5-8 (as you don't have Consult II). Step 9 is the most important, to "Check continuity between closed throttle position switch terminals 6 and 5 under the following conditions:

Insert a 0.05 mm (0.0020") and 0.15 mm (0.006") feeler gauge alternately between the stopper and throttle drum
as shown in the figure.

Continuity should exist while inserting 0.05 mm (0.0020 in) feeler gauge.
Continuity should not exist while inserting 0.15 mm (0.006 in) feeler gauge."

You'll have to rotate the switch to find the right position in which continuity exists with the thinner gauge and does not exist with the thicker gauge. Make sure you're reading the continuity of the correct terminals on the correct connector. Don't use too large of a voltmeter probe, otherwise you'll expand your terminals and they won't seat correctly.

Then reset the idle memory per step 12.

It might idle correctly after performing these steps. If not, you'll have to perform the Idle Air Volume Learning on EC-70. It's a somewhat complicated procedure and you'll have to follow it to the letter. If you go this route, take care to use a stopwatch to time how long you drive the car to warm up the transmission, as this makes a difference in whether the procedure is completed.

If you need to repair the ECU, there are plenty of folks on eBay that do it for a reasonable fee. If so, you'll also have to replace the IACV and TPS, go with Hitachi. Good luck, keep us updated.

The tps stop screw was not touched, has lined up undisturbed paint on it. I tried adjusting the throttle cable wouldn't idle without holding open the throttle plate. I could try the volt meter test if I put the ecu back in. Replaced the iacv already. Recently new pcv, leaky valve cover gaskets, manifold gaskets, some cracked vacume/ breather hoses.still same problem. I got a scan tool that can perform the relearn and no luck. It will idle temporarily after the relearn then drop. Took out ecu, no visible damage.

After lots of research it seems some people have had the same problem and not be able to do the relearn. Even with consult. I'm sure it's gotta be the chip controlling the iacv. A mosfet at location ic17 on the board. Apparently it goes without any sign of damage when iacv goes, and sounds like my leak was quite developed.

I can't find this part online anywhere.
If I could find that chip I could have it done for 50$ from local repair guy. The letters are to worn to fully read off the part number. Anyone know of a place to order that part?

Anything marked "IC" on a circuit board isn't usually a FET or transistor, those are usually labeled "Q". IC is just "Integrated Circuit" and can mean a lot of things, but in a 3-pin package that looks like a transistor, it usually means a voltage regulator or voltage reference. That could explain the ECM losing its backup brains if it's the LDO for the backup memory. It could also be a serial EEP, which would also neatly explain the brain drain. Your only hope is probably to find a unit with intact case markings, or maybe contact a rebuilder and see if they're willing to identify it for you.

Oh I see wow thanks for the quick reply, you know your ecus! I read a couple ppl were able to source the part, one guy called it a mosfet but they diddnt give the part number or link. Zoomed in on a pic of the part i can make out most of the part # but not getting anything on google from any of the variations ive tryed. Possibly a burn speck visable. I'm going to call some ecu repair places around canada and see if I can find anything better than the 350$ I found online in Ontario. Seems like a lot for a 15$ part and 30 min of work. I would love to use ebay but everyone listing ecu repair is in states as well as most of the ecu specialists it seems. Last time I got something shipped over the border it took forever and was a hassle.

That's not a transistor package, it's what the industry calls a SIP (Single Inline Package). That's undoubtedly why it's hard to find, nobody uses SIP packages much anymore. They were a way to save board space back in the transition days between through-hole and surface-mount when multi-layer circuit boards were pricey and sometimes unreliable. With 10 pins, my guess is that's a 4-channel FET array or a stepper driver. NEC made both, and what's left of that logo is definitely NEC. The bulge near pin 9 definitely looks like a meltdown. You could contact Renesas, NEC spun off most of their silicon operations to them in 2010. One trick you can try for reading the numbers is cleaning the surface with alcohol and then shining a flashlight slantwise on the surface so you can see the impression rather than the ink. If you can get the numbers, there are a lot of parts houses in the Far East that specialize in locating out-of-production and obsolete silicon. Send out a few emails and see if you get any bites.

I believe the part you are looking for is a MOSFET- a NEC STA509A, which is IC17 on the board and typically gets taken down when the IACV shorts out. You can get a Sanken replacement for that from many sources.

Yep, that's definitely the right package. It's a quad MOSFET array. The Sanken part is also out of production, but I see plenty of them still around. Here's a link to the datasheet:
https://www.semicon.sanken-ele.co.jp/sk ... _ds_en.pdf

Kobierski wrote: ↑

Sun Mar 10, 2024 9:32 pm

Oh I see wow thanks for the quick reply, you know your ecus! I read a couple ppl were able to source the part, one guy called it a mosfet but they diddnt give the part number or link. Zoomed in on a pic of the part i can make out most of the part # but not getting anything on google from any of the variations ive tryed. Possibly a burn speck visable. I'm going to call some ecu repair places around canada and see if I can find anything better than the 350$ I found online in Ontario. Seems like a lot for a 15$ part and 30 min of work. I would love to use ebay but everyone listing ecu repair is in states as well as most of the ecu specialists it seems. Last time I got something shipped over the border it took forever and was a hassle.

A few years back, I helped someone out on this forum to figure why his '02 Pathfinder wiring from the IACV to the ECU did not match the circuit diagram in the factory service manual and why he found a NEC PA1560H, like you have, instead of the Sanken STA509A MOSFET in the ECU. I did confirm on my '02 that I had the same wiring difference compared to the FSM, with different color wires landing at different connector locations on the ECU. We had the same ECU number MEC14-345 C1. I did not open my ECU to see if I have the same NEC MOSFET, instead of the Sanken MOSFET he expected to see on his but I supposed it was and that Nissan made a change after the manual was published. The circuit of the Sanken MOSFET is a little different than the NEC MOSFET circuit so I supposed that might have had something to do with the wiring difference of earlier made '02 Pathfinders and before '02. Just a guess, and I am not technically savvy with this level of electronics, but functionally the Sanken MOSFET might not behave the same as the NEC MOSFET if your "02 wiring from the IACV to the ECU is also different compared to the FSM. I'm not really sure about that. In Canada at Amazon.ca the NEC MOSFET is available. https://www.amazon.ca/MachineMid-UPA156 ... B09PLP6W49

Here are the Sanken and NEC MOSFET specs.
https://pdf1.alldatasheet.com/datasheet ... 1560H.html
https://pdf1.alldatasheet.com/datasheet ... A509A.html

mdmellott wrote: ↑

Thu Mar 14, 2024 9:32 pm

A few years back, I helped someone out on this forum to figure why his '02 Pathfinder wiring from the IACV to the ECU did not match the circuit diagram in the factory service manual and why he found a NEC PA1560H, like you have, instead of the Sanken STA509A MOSFET in the ECU.

That has to be a difference in the circuit boards, Md. The pinouts for the two parts are identical and I don't see any functional differences that would matter in a 12V stepper-driver application like the IACV.

Thanks for the info guys. You found the mosfet!!! Damn I already decided to send it to an ecu repair shop, 350$ was the best price I could find shipping included. Some places were double that. I'll post an update after ecu is back.

Kobierski wrote: ↑

Fri Mar 15, 2024 8:31 am

Thanks for the info guys. You found the mosfet!!! Damn I already decided to send it to an ecu repair shop, 350$ was the best price I could find shipping included. Some places were double that. I'll post an update after ecu is back.

Unless you have good soldering skills and good soldering tools, that isn't the sort of job you want to take on anyway. The designers purposely leave a lot of copper on those circuit boards to help heat-sink power parts like that FET array, so unless you have a good high-wattage iron with bullseye tips, getting the pins out without damaging the pads can be a chore even when you first cut away the old part. Definitely not a job for the fainthearted or inexperienced.

I was thinking I'd bring it to a local electronic repair guy if I found the mosfet. 50$~ an hour. But this way it's done by the pros, they will test everything and I get a warranty! Should be back soon they have same day turn around. I used xemodex.ca they have a location in the states as well

It was the ecu, it came in the mail a few days ago, got it installed and after having the same issue (having to hold the gas pedal to idle) for first couple start ups it began to idle normally. Test drove 10 min, performed idle relearn on my new scantool and the issue is resolved! Been idling at perfect rpm consistently the past couple days.
Thanks for the help and info great community. To anyone having similar issues and had an iacv leak on one of these engines, don't hesitate to repair the mosfet NEC STA509A or Sanken STA509A. Might want to check which you have. Ordering the part and replacing at an electronic repair shop will cost you a total of 60-100$. Or ship it out to an ecu repair shop for an arm and a leg.

https://www.amazon.ca/MachineMid-UPA156 ... B09PLP6W49