2013 Freightliner M2 106, can you replace ecm with used one?

Engine ECM's seldom fail but they do on occasion. Allison TCM's do fail I have
replaced quite a few. The ECM and TCM will very likely need to be programmed
as there are so many parameters that can differ between trucks.

 

Agreed since the same PN is in a bunch of similar vehicles, they pretty much all need to be programmed now days and the DD software checks/pulls updates for each of the modules.

Unless you were fiddling with the TCM, they don't generally change parameters/calibration, and from your question it sounds like you haven't messed with it. The 2 could only really become incompatible if something got replaced and it wasn't designed to work with the other module for some reason (New ECM looking for manual but old was Auto/AMT), or sometimes an update causes compatibility issues and then a new update is made to fix that. (Snake Eating It's Own Tail situation)

 

Changed a couple ECMs before, failure is very rare but does happen. Always download the parameters and programming from the current unit and upload it to the new unit.

99% of the time its not a simple plug and play deal, even if its a brand new ECM. Quite often parameters get adjusted by owners to suit their needs over the years. Even if purchased and programmed based off the VIN it may need a few adjustments made to have it operate the way you need it to.