You will need to have it programmed by a shop or dealer with ob2d programming software (Launch X431 we recommend). Your VIN# must be added to it along with linking your car key immobilizer or it will not work! This would be the case on any ECM you buy, used or new.  The immobilizer and VIN# have to be added to the ECM or car will run for seconds and turn off. 
You do not need new keys etc - this is not true. 

Up for sale is a factory new OEM ECM/PCM - not a mile on it.  

Only fits what is listed below. No miles on it! 
 
Fits: 2001 Pathfinder - 4x2 or 4x4 - Manual Transmission 
 
The number on your old one must match: 
23710-4W011
23710-4W012
23710-4W013
23713-4W011
23713-4W012
23713-4W013
 
Hitachi number is MEC14-183

INTERNATIONAL BUYERS! PLEASE NOTE! Buyers of items shipped outside the USA are responsible for customs fees/taxes/duties and may encounter delays due to customs inspections. PLEASE be aware of this!