No Ranging Response received - T3 time-out and disconnects

The upstream power is too high / out of spec. That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, latency problems, and the un-bonding of channels.

In an effort to try to obtain better connectivity / more wiggle room, check to see if there are there any excess/unneeded coax cable splitters in the line leading to the modem that can be eliminated/re-configured. Any splitters that remain should be high quality and cable rated for 5-1000 MHz, bi-directional, and no gold colored garbage from Radio Shack, Home Depot, Target, etc. Splitters should be swapped with known to be good / new ones to test.

Also check the coax cable for any damage such as cuts, nicks, abrasions, kinks, sharp bends, etc.

If there aren't any unneeded splitters that can be eliminated and if your coax wiring setup can't be reconfigured so that there is a single two-way splitter connected directly off of the drop from the street / pole with one port feeding the modem and the other port feeding the rest of the house/equipment with additional splits as needed and you've checked all the wiring and fittings for integrity and tightness and refresh them by taking them apart then check for and clean off any corrosion / oxidation on the center wire and put them back together again, then perhaps it's best to book a tech visit to investigate and correct.

Good luck with it !

Thank you EG! I Was hoping you would find my post! I have not changed any connection settings from where my system has been over the last 2 years. Xfinity said they did "advanced repair" taking two hours this morning (the work was digital) and I am still seeing the T3 Timeouts. Would that still indicate that having a tech come out be the best solution?

The power levels can't be adjusted or fixed digitally or remotely. It takes a *boots on the ground* physical intervention. That said. If there is nothing that can be done to improve the connection quality, then you'll need a tech visit as stated. 

Bear in mind that if the premises facing techs can not find or fix a problem at your home, it is they who are responsible for escalating it to their line / network / maintenance dept. techs. The problem may lie beyond your home in the local neighborhood infrastructure somewhere but it is their S.O.P. to start at the home. And if the problem is found to be on their side of the demarcation point, there will not be any charge.

As a follow up, a tech came and removed an old Direct TV splitter he found in our line. He also replaced the line from the box to the house and our power levels now look really good. However I am now dropping signal with a new error: MDD message timeout. I Will be opening another ticket regarding this, unless I can ask about that in this thread as well?

Thanks