I assume transmission control module. See link at
http://www.greendieselengineering.com/f ... st/91.page for where it is an such. How it could be loose beats my; when I removed the plug to send my TCM to GDE for their tune that plug was on REALLY tight. That said it's possible you have a weak/corroded connection there that might be improved by loosening the plug a bit, wiggling it a bit, and then tightening it back down. If you try be very careful retightening that 8mm hold down bolt as its other end goes into a nut in a plastic housing; over tightening can "spin" the nut in that housing making future removal a real chore. I found it best to firmly wiggle the plug back into place while gently tightening the 8mm bolt until the plug was obviously fully seated and the bolt was just snugged down with no additional pressure applied to the bolt.