# ECM serial number breakdown/decode?



## Gumby75 (Jan 13, 2013)

Hello:

I have a friends 2004 altima 2.5L that I'm replacing the ECM on. It was originally a crank/no start problem - only codes present were P1122 & P1126 for the throttle control motor circuit. After further testing, I confirmed the ECM was not commanding the throttle motor relay to turn on and supply power to the throttle control motor.

I've confirmed good battery power to the ECM via all appropriate pins & ignition switch positions as well as good ground connections. The ECM connector is in good shape and there's no evidence to indicate loose or broken connections. Crank and cam signals are good. As far as I can tell, the ECM is receiving every signal and source voltage it's supposed to "see" to start and run the engine, but it's not working; ergo, I'm replacing the ECM.

What I'm curious about is the decoding of the ECM serial number. I've found all kinds of "matches" on ebay, but without being certain about what the serial number means, I don't want to waste time, effort and money on a replacement ECM that won't work for this car.

The current serial number on this ECM is: MEC35-020 D3 3X29

Almost every ECM I find listed on ebay has the "MEC35-020 D3" on it, but the last 4 digits vary greatly. I saw "3Y12" and "3826" as examples - I even found one that had "3X28" on it - but without knowing what those numbers are supposed to mean, I don't want to chance buying the wrong one.

So can somebody *please* break down these last 4 digits for me? If they mean nothing, all the better - but if I need to look for specific replacements, obviously that's useful to know. 

Thank you.


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## Shut-Trip (Oct 18, 2012)

Gumby75,

you said Quote: " I don't want to waste time, effort and money on a replacement ECM that won't work for this car." so along that though process.....I offer my humble advice:

If it were me, I would be over my head in this problem, so I would be thinking worst case senario / and ouotcome. 
So assuming that you find the code for the ECM, how can you be sure that the ECM purchaced from e-bay is fully functional?

In my opinion, I would make a trip to the dealer, and get a quote from them for:

Quote 1: Complete Repair / replacement of the ECM, and Test Fuctionality of car.
Quote 2: a brand new ECM for the VIN number on your customer's car.

Then ...let the owner ( your friend) and owner of the car decide which way to go with the repair. Afterr all, he has to pay for the ECM and presumably pay you something for your time...

Good luck


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## Gumby75 (Jan 13, 2013)

Thanks for the advice.

We've already looked at replacing it with a new ECM. The bottom line is that it's a money issue - they've just had a baby and, although they can afford it, he doesn't want to sink a bunch of money into this car (it's not the only car they have, so this isn't an emergency situation either). Furthermore, it's a spare time project for me, so I really haven't put an extensive amount of work and time in on it (maybe 10 total hours over the last few weeks).

While I do agree that there's no guarantee a replacement from ebay (or the local pick'n'pull) will work, in theory almost any ECM from the same year/model/engine would make the engine run. I'm hung up on the serial number because I'm thinking that the last 4 digits indicate specific options or programming. It could be something as simple as cruise control, which wouldn't matter just to get the engine running - or the difference between a manual and automatic transmission, which is going to affect how it communicates with the TCM.

Like I said - the serial number on the existing ECM ends in 3X29 - and one possible replacement I found ended in 3X28 - so these are virtually identical ECM's except for one thing - and it's that difference that I'm trying to figure out.

I have limited access to factory service information (Alldata & Mitchell) but for all the searching I've done on those sites (and google and yahoo and "nameyoursearchengine".com) I can't find specifics on what these serial numbers are supposed to identify.

I'm sure this information is available, it's just a matter of finding it....


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## smj999smj (Jan 1, 2006)

Being that these are programmable ECM's, I wouldn't think it mattered what the serial number is. You'll want the latest program, which means you'll be going to a Nissan dealer anyway to get the part number checked out and updated, if needed (or, at least that's what I would do). Also, I'm not sure if they were still programming the key to the ECM or BCM in 2004, which is something you'll want to check on. If it's coded to the ECM, you will not be able to start the car with the replacement ECM, new nor used, until the keys are registered with the replacement ECM. This needs to be done by a Nissan or Infiniti dealer or a locksmith that has the equipment to do so.


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## Shut-Trip (Oct 18, 2012)

That s a noble cause:

you can check the value of the car on:

Kelley Blue Book

I was equating the replacement of the ECM as being similar to brain surgury for a car. therefore thinking in terms of uncertainty of the outcome. 

I would just check with the local dealership, and they can tell you the code;

most serial number , as well as VIN numbers there is a method to the numbering system.

like a VIN number the last charactors in the number could very well be just the number of the unit off the assymbly line, and thus insignificate.. confirm with a reliable, and experienced Nissan parts guy, like my pal at Ferman Nissan.


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## smj999smj (Jan 1, 2006)

I don't think most dealers could tell you much about the serial numbers, personally. They really have no need for the information as they go by Nissan part # and have no use for the ECM manufacturer's part numbers or serial numbers. They might get the info from a Nissan part rep, if they are the type to go really out of the way for a customer. There was a TSB released a long time ago that had ECM serial number information, but it was well before 2004 and one might be hard pressed to find it now.


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## Gumby75 (Jan 13, 2013)

If a used one will most likely need programming too, then yes, it makes sense not to get hung up on the serial number.

I will speak to my friend and inform him of his options.

Thank you all for your info & direction on this.


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