Am looking for a ecu A18-631-504 for my standard-Does this number have to match exactly-found one but last 3 numbers are different

Forget all that. Get your existing ECU repaired. It is a printed circuit board with components that fail. You just replace the components.

https://www.google.com/search?q=ecu+repairs+near+me

..

I don't know for sure but I think the ECU will need programming with the vin-sensitive security code(s) and possibly other information that is exclusive to your car.

The so-called flashing is used to instal software patches and fixes in service when problems are encountered. Unless you are unlucky a new or official replacement ECU should already be loaded with the latest software version, but again the dealer should be your first port of call to ask such questions and then maybe compare notes and prices with a few local specialists..

I suggest you check with the dealer and ask if the part number has been superceded, or if the unit has been modified in the last ten years.
If there are no changes to the spec, the replacement ECU should have exactly the same part number as the original.

2006 Nissan Sentra Service Repair Workshop Manual INSTANT DOWNLOAD


for the easy solution download the pdf file

No they change as the module is updated.

ECU TOPIC (swaps)
why ask us? we can't see car, or see what drive line is there. nor VIN code.(telling same)
why not ask JEEP.?
amazing ?

ever seen this?

http://www.factorychryslerparts.com/productSearch.aspx?&ukey_make=1064&ukey_model=15529&ukey_trimlevel=0&ukey_modelRange=0&modelYear=1999&ukey_category=0&ukey_driveline=0&isOnSale=0&searchTerm=



computer, ,that is the ECU, and is not the only computer.
here are the ECU rules. (not full, only jeep knows all rules)
it must have same base number.
then needs to be programmed to match your cars, drive line and federal smog laws and year.)
end story.

absolutely , the numbers have to match exactly !

The firing order is 1-3-4-2
looking at the engine from the front of the car, number 1 is on the left side then number 3 is the 3rd one from the left then number 4 is the last one on the right then number 2 is the 2nd one from the left.
The coils should have numbers on them, match the numbers with the firing order.

If you can find the exact car in the scrappers as a runner then take all the parts off that and it will run .Numbers ?? ignore it as you have an identical car but a different model will not work without being remapped

You have to contact the Smart dealer in your area , so that they can rectify the problem , as Chassis number is saved into the ECU too and can be extracted from the car ECU it self to show the original chassis number, assuming it has the original ECU in it. Or you can check with any shop that aervice Smart for the same. By the way before you do that, which VIN does not match , the sticker in the back or the engraved one in the front??

Yes , I would have the ecu reset to factory standards.
You never know if some one changed the ecu to run a racing engine. There are all kinds of software that people can get to make the engine run at 150 or more horsepower past factory standards.