I am hoping someone can educate me on engine computers for these. I bought an 01 Pathfinder with 3.5, A.T, 12/00 mfg date, with all mode 4x4. I bought this without an engine computer, so I don't know what part number was in it. When I look it up on Hollander, it says the computer number is 23710-4w020. But when I try to find one at the wrecking yards, nobody has one with that number. Everyone that has one with these options and date range has an MEC number. I am finding mec14-340 B2 0906. Another is MEC14-340 B2 0Y06. Or MEC14-340 B2 0925. Or mec14-343 A1 8327. Or MEC14-340 B2 0807 (and several others). I want to buy one that is correct and will work. But I don't know how to figure out what will and won't work. There are 27 different computer options, and apparently these 4 will work:

PATHFINDER 01 Electronic Control Module, 4x4, AT, from 8/00 thru 1/01, w/o all-mode 4x4 system; ID 23710-4W020

INFINITI QX4 01 Electronic Control Module, from 8/00 thru 1/01, ID 23710-4W020

PATHFINDER 01 Electronic Control Module, 4x2, AT, 3.5L, from 8/00 thru 1/01, ID 23710-4W020

PATHFINDER 01 Electronic Control Module, 4x4, AT, from 8/00 thru 1/01, w/all-mode 4x4 system

But since nobody has the computer with the correct number, I don't know what to do. Most of them start with mec14-340 B2. That seems to be the most common number, but these are around $150 for a used computer, so I don't want to buy the wrong one. Can anybody educate me that knows about these? Any assistance would be appreciated. Will be in Florida for a mini-vacation to get out of the Minnesota deep freeze from friday-monday. So I may not be able to respond immediately

The 23710-4W020 is the actual Nissan ECM part number. It is really more of a number for the ECM program than just the ECM itself, as 2001 Pathfinders had programmable ECM's. FYI, even if you get the ECM, it still won't start because you will need to initialize the keys to the ECM otherwise the immobilizer system will not let the fuel pump operate and the security system will stay on steady. The MEC number is a Hitachi part number; Nissan did put out a service bulletin with listings for the ECM Hitachi and Nissan part numbers, but it was a long time ago and I don't have the information. One of the reasons they don't put the Nissan part number on the ECM is because of it being a programmable part. If software updates are made to correct a particular problem, the ECM part number will change. The only way to really get the part number of the program that is on a particular ECM is by using a capable scantool. Have you tried Car-part.com? They are a listing base for auto salvage yards and some of the listings with have the Nissan P/N or MEC number, or both.

Good information. Thank You! Yes, I have checked car-part.com. That's where I was finding the mec number. It sounds like what you are saying is that I just need to buy one. I saw someone selling the computer with the immobilizer... That might be the way to go. If I am hearing what you are saying, that should take care of all of the issues so that I don't need to do anything else. Otherwise, is a Nissan dealer the only place that can initialize the keys to the ecm? And flash the computer, if it needs a different program than what is on whatever computer I buy?

There are some locksmiths that can initialize keys. It's an expensive investment for a locksmith so all of them don't have the equipment to do it. Just the same, there are some shops that can reprogram ECM's, but it's also an expensive investment and requires a subscription service as ECM's are routinely updated. It would probably be easier to just have a dealer do it than try to find an independent shop that has the ability to do it. Also, having the immobilizer does nothing as you need the key, and then the key will obviously be different than the ignition lock and door lock coding.