Anyone fimilar with 9400i 870cm

[Waterloo]

Here are all of the circuit schematics from Navistar, I did not see your truck, but that does not mean it is not there...

Link one, to schematics http://bodybuilder.navistar.com/General/BBcircuitIX.htm

Link two, this is the main site for Navistar Body Builder where you will find even more information... http://bodybuilder.navistar.com/General/Home.Htm

This should get you pointed in the right direction.

For Cummins, https://quickserve.cummins.com/info/index.html

Engine serial number and register it.