Originally Posted by blackhat620
You basically answered your own question. The FMC TBC has a very good and sensitive diagnostic system built in. Generally when it finds a problem like you are experiencing, it is a loose wire on the trailer or more commonly a bad ground on the trailer. Grounding through the trailer ball is a **** poor system and the FMC TBC will detect when there is a minimal or no ground situation. Your trailers get used and abused in there everyday work, make sure all wire connections are tight on the trialer and that good grounds are installed on the trailer side and connect to the connector on the trailer side.
Hope this helps
I think the controller is bad. I have hooked this truck up to 5 different trailers and it has given me the same error on all of them. My 350 has also been hooked up to all 5 and I only get the disconnected message on 1. Another 350 with aftermarket has also been hooked to all 5 and worked fine.
Guess what I did all morning.
I am thinking the sensitivity is the problem on the one trailer that I am having issues with on both TC's. The weird thing is, when I use a circuit tester, it works fine, no check trailer, nothing. Hook it to a trailer and BAM. The other strange thing is when I disconnected any of the trailers the display was flashing the red trailer icon and the gain number. My 350 just goes blank.
Thanks for the advice. If the sensitivity is the case, they need to dumb it down so it isn't, because this is ridiculous. Had I known, I would've stuck with an aftermarket, but I liked it so much in my 350 I added to my 550.