I have done that solution with a self resetting circuit breaker cost .59 parts wise

 

What/how/where exactly did you do it?

 

pin 3 is the signal pin so cut the trace and bond and solder a smt resettable

 

Could you please elaborate so that all of us can learn from you:

• OK, you cut the trace leading to pin 3; on the ECU or on the IACV? (both have pin 3 ... ) My guess is you did it on the ECU, correct?
• You soldered in a resettable circuit breaker ... something like one of these http://www.delcity.net/store/Circuit-Breakers/p_3 ;
• How is it working for you - anything you can share?

Thanks in advance!

 

http://www.digikey.com/product-highl...md-fuses/50555


No this is what i used

 

Btw avpro wont repair burnt board traces

 

How did you add your PTC fuse to your ECU board? - and don't be so stingy with words

 

I still can't find any close-ups of the burned paths from the underside of the board where the STA509A chip goes. I tried emailing those Ebay "repair" dudes and they have not replied....and I kind of doubt they ever will.

I also went to the yard this past weekend and I thought I scored a ECU but someone got there before me..ergh!

Anyhow, I'm willing to PayPal some cash just for some high resolution pics.

My ECU is for a 2001 Infiniti I30t Automatic (same as a 2000-2001 Maxima), 3T A56-Q79 ZA0

Help!

 

[img=http://s22.postimg.org/4psw6wiq5/image.jpg]

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Nice work!
Do you have a circuit diagram for the board, or did you do it without a diagram?
And btw, I still can't tell where you put your fuses ......

 

Thats a customers unit for a MT trans i dont use them on all there are only 3 units with resettables out there as test subjects.

 

When the IACV is malfunctioning and causes 15 amps of current to pass through the ECU circuit it will fry the STA509A chip and the circuit board. (red arrows represent 15a of current)





It has been years since I worked on this problem, in retrospect I would think the best place for fuses would be inline fuses in the wiring harness right before the bulk connector to the ECU.( the 6A fuses would be the modification)

 

Very good Nakis - this should work.
This is also what I have been thinking. However, I still see two issues:

• To insert the fuses, you would have to splice the wiring harness just before big/bulk connector plugging into the ECU. Then, split the proper wires (without making a mistake) add/solder in extension wires and lead them to the fuse box, where you would place the fuses. That way, the fuses could be easily replaced. The problem is - there is a lot of room for error, and the modified harness will forever be a bit fragile.
• The second issue is that this does not take care of the electronic mounts. You could go with similar solution, adding in-line fuses to wires connecting to ECU terminals #49 and #50. Alternately, you could perhaps insert the fuses at the Joint Connector (after JC-12, at F18). Not sure what fuse size to use, but one could try 6A and experiment.

I have been thinking about all this for a while. I have implemented Coolant Bypass, and I have my Electronic Mounts disconnected, so I have some protection but I know it's not 100%.

Edit: What about placing the fuse (just one fuse) in line with terminal 3 of E15/F13? This would much simpler, but I am not sure whether this would work (not without having the ECU diagram). Your solution is guaranteed to work ... .

 

If you want to run everything to the fuse box easier to change the power source and this is the way Nissan should haveran it with two separate fused power sources. (only problem I can for see is that the fuses might easily blow)

 

This implementation (or some minor variant of it) is promising. It is the least destructive in terms of cutting/splicing existing harness - one only has to isolate pin 5 of the IACV connector, and power it via the new fused wire.

I wonder what would happen if I just replace the 15A fuse (at #58, picture in the earlier post) with 6A -10A fuse; leaving everything else "as is". This may be a worthwhile experiment ...... I may try it when I get some free time and a bunch of low-Amp fuses. Also, I would like to find the location of the splice that feeds power from the ECM relay (E15/F18) to pins #2 and #5 of the IACV.

 

Fixer, you have pics of the backside of the board, not the top? My top side paths are ok. It's the back side of the board where the 509A pins stick out that are screwed up. Thank you!

 

Sorry only have that one.until a new unit comes to me.

 

This is a follow-up on my post #175 in this thread: I replaced the 15A "IACV" fuse (at battery feed, #58 in Fusible Link and Fuse Box) with a 7.5A fuse. So far so good, no problems whatsoever after one day of driving. If the 7.5A fuse keeps working, I may even try a 5A fuse. In theory, it should work: At 68'F, each IACV half-coil draws about 0.55A, or 2.2A max for all four coils; this leaves 3A margin for lower coil resistance at cold temperatures and other errors.

I still wonder about: a) How much does the resistance change with temperature?, and b) Why did Nissan choose the 15A fuse - they must have had a reason, unless they didn't think this through? Also, I need some cold weather to test this properly ....

At any rate, this fuse replacement may turn out to be on of the easiest ways to improve the protection of your IACV/ECU. I will let you know how it goes.

 

I don't think resistance will change much within sensible range. It decreases by about 8% for every 20C degrees fall in temp. The most likely reason for the chip to go out is a short in one of the coils. This might not even change resistance by much but will drastically reduce inductance (x100 times easily) and that can easily overload the chip. Nissan most likely put the fuse to prevent wire from catching fire, not to save the driving chip.

 

Max_5Gen, thanks for your comments. I understand your points but we have a bit of crosstalk. Let me re-phrase what I was trying to say:

• With the OEM design, when the IACV fails/shorts, up to 15A of current can go through the circuit and fry the ECU.
• How come Nissan has not provided a better protection? Why use a 15A fuse when a 7.5 fuse is doing just fine? (I have been now driving with 7.5A for 10 days).
• If my experiment confirms that the IACV works properly with a 7.5A fuse (or perhaps even 5A fuse), all of us should switch to this lower-rated fuse ASAP.
• Without ECU circuit diagram, I can't say that this is a guaranteed protection, but it certainly is an improvement.

I understand your point about inductance but I think it's irrelevant to my argument. More in a PM to you (coming).

 

IMO, Nissan is protecting wires from catching fire, not the ECU, that's why they used 15 A fuse.

BTW, if ECU drives coils as resistors it would give max current through that fuse from the stepper motor operation around 2.6A: 14.4V/22 Ohm and multiply result by 4 as 22 Ohm is the resistance of 2 coils in series and 2 of them are energized at the same time in parallel. If it drives them as inductors (using short pulses to the ground but not holding windings to the ground for long time) the max current would be even less. My point is 3A fuse is probably a minimal fuse which would survive there.

 

Really? Well, a 7.5A fuse (or 5A fuse, whatever the case may be) will protect BOTH the wires and the ECU. What am I missing?

I very much agree. It's a stepper motor, so there is pulsing (and you can hear it when you shut off the car). I wouldn't go below 3A, but I'll be switching from 7.5A to 5A tomorrow.

 

You're most likely not missing anything. I was just trying to explain why they selected this particular value for the fuse. From Nissan's point of view fried ECU is not a problem until it is proven otherwise and becomes subject of another recall.

Unfortunately, I don't know how exactly ECU controls the motor and it would be hard to distinguish between 2 modes I mentioned by the sound of operation- both would sound the same. The difference is in the stationary state when motor is not moving- I have a feeling ECU doesn't have to drive 2 out of 4 coils to the ground in order to maintain motor position but I could be wrong here.

You should be fine with lower fuse as long as nothing else draws the current through the same fuse.

 

No, nothing else draws a current through that fuse. That's what the wiring diagrams shows (see FSM/EC-432; post #172 above has a copy).

So, I should be fine. So should be everybody&anybody else who implements this improvement. I am just very disappointed with Nissan - what an example of poor engineering, causing so much trouble and large expenses to many Maxima owners !!!

 

I have been trying to improve the fuse protection for the IACV/ECU. Here is a progress report.

In most instances of IACV failure, the STA509A transistor in the ECU is fried. According to its spec ( http://www.datasheets360.com/part/de...4356475109966/ ), the STA509A can sustain a maximum steady current of 3A, and maximum pulsing current of 6A. I have been trying to find a fuse protection that would be both simpler and better than what Nakis did (he added 6A fuses to the ECU; see his earlier post https://maxima.org/forums/5th-genera...ml#post7013275 ). The STA509A data sheet tells us we need to limit steady current to 3A, and pulsing current to 6A for each IACV feed (#3 and #5). Also note that typical resistance of each IACV half-coil is 20-22 Ohms; consequently, under normal conditions the current through each half-coil should not exceed 14.5/20 = 0.75A, or 3A total.

Keeping the existing OEM wiring intact, I started by questioning the choice of the 15A "IACV" fuse (see https://drive.google.com/file/d/0B6O...ew?usp=sharing ). I have tried the following fuses and got the following results:

• 3A - blows out almost immediately, when driving out of my driveway. Got P0505, etc. (This shows that the IACV draws more than the 3A derived by the steady-state analysis above).
• 5A - the current subject of my experiment; it has been in and working fine for almost two days.
• 7.5A - this fuse did work without any problems for two weeks.

The above suggests that 7.5A fuse and perhaps even 5A fuse may be a better choice than the OEM 15A fuse. This fuse replacement is very simple ($0.75 for the fuse and 30 secs of your time), but without modifying the wiring harness, it does not guarantee that the fuse will blow up before the STA509A will.

To limit the current through each STA509A driver, we would have to modify the wiring harness as shown in this picture: https://drive.google.com/file/d/0B6O...ew?usp=sharing. Moreover, we still have a potential "steady state 3A" vs. "pulsing 6A" load problem. I am pondering the use of PTC breakers (http://www.digikey.com/product-highl...md-fuses/50555 ), or doing more experiments with traditional fuses and some harness mods.

I am not sure what I'll do next ... appreciate your comments.

 

Isn't it easier just to unplug the motor mount and move on with life?

 

You have a point but there must be a better way (than what Nissan did). More important, this isn't about motor mounts, this is about the IACV !

 

It's a chain reaction that can be sourced to the electric motor mounts, yes?

 

i don't remember reading that, i thought they were 2 separate issues with similar consequence. could be wrong tho

 

Yes, the IACV and the eMounts are two separate issues. Either can damage your ECU; the IACV through ECU pins #(6,8,7,and 17) and EMounts through ECU pins #(49 and 50).

 

According to Nick at Avpro, they fix a ton of burnt traces and created their relay bypass just for our specific ecu issue

 

Thats what I do..along with both new gaskets + heavy gasket paste..Never had one come back and been doing them for over 6 years now.

 

You are talking about the IACV gasket, right?
What tools to you use to tighten/unscrew those Phillips screws? - they need to be quite tight for the gasket to hold.

 

Has anyone tried this software to reprogram keys and the iac learning?http://www.nissandatascan.com

 

Yes...

 

Wow, this is great! Thanks for the info!

 

OK, here is another update: The 5A fuse blew out after two or three weeks. It blew out when when I tried to start the car without waiting the 2-3 seconds I usually take to let the fuel pump prime and to let the IACV position itself (just my hypothesis). I am back to the 7.5A fuse; not a perfect protection but certainly a bit better than the original 15A.

As noted earlier, I know what the proper solution is, but I am still hesitant to muck around with the harness, cut/replace wires, etc.

 

Oan the unit i installed the self resetting smt breaker in is going strong 5m 2w now

 

UPDATE (it's long):

I gave up on the original ECM as replacing the burnt chip as tracing and fixing the broken paths did not fix the issue for me.

I bought a used 3T ECM on eBay (120.00). I bought a used TB (included the IAC) for 23.00 bucks at the local pickyourpart. It was off a 2000 Maxima and looked to be in newish shape. My car is a 2001 Infiniti I30t. The only difference I saw was a valve sitting on top of the TB. I unbolted it and closed off the small tube that went to the TB. I also got a new TB gasket from the dealer for like ~5 bucks.

The next issue to tackle was the programming of the key and IAC learning process. I called the closest Nissan dealer and they said they would not program my key because my car was not a Nissan (whatever). The Infiniti dealer was just too far and tow would be too expensive!

That's when I started searching for a OBD software that could potentially perform the key programming. I ran into the Nissan Data Scan II for Windows. After some researching, I decided to buy it for 69.99. I purchased a cheap OBDII scanner for under 10 bucks on eBay as well. I dusted off an old lap top running Windows XP and installed the software.

The key programming literally took 10 seconds. I used the master pin that appears to be in many places online.

The car started right up!! I let it warm up for a few minutes and even drove it around the block a few times. The idle was still high but I had not performed the IAC learning yet. The software also can do this. I followed the instructions for this and voila...idling leveled off at ~700 RPMs. The car runs so smooth now!! Finally!!!!! I have been driving the car for the past week days with no issues.

BTW, I also disconnected the motor mounts, performed the TB coolant bypass and replaced the 15 amp fuse (#58) with a 7.5 one.

A sincere thanks to all of you for helping out with this thread. If you are in the San Diego CA area let me know and you can use my laptop with the NDS software and OBDII plug.

 

Congratulations on your success! I have both NDSI and NDSII. I've used NDSII on a friends 5th gen. Unfortunately I can't use NDSII on my 99 model with NATS. For the 5th gen I use a $10 eBay VAG 409.1 OBD2 cable.
Keeping a running copy of NDSII around for a 5th gen is good way to save money I think.