2007 freightliner M2 106 issues

Hey I have a freightliner M2 106 with the Mercedes mbe900 and it has a Allison 2100hs transmission! I had the transmission replaced by a friend and I’m having some issues I think the transmission is in limp mode or 3rd gear! Reverse works fine but fwd not so much I’m trying to figure out why it’s in limp mode so I crawled underneath to see if anything was unplugged or not installed correctly and I found a sensor that comes off the 2 hoses coming from the transmission the connector is missing I can’t find the wire anywhere would this cause the transmission to go in limp mode?