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theperson88's avatar
New Contributor
4 years ago

T3+T4 Errors with High Uncorrectables - Intermittent Internet Cutouts


I'll try to keep it short - I've been having severe internet issues (periodic cut-outs 1-2 times an hour + 2-20% packet loss). I found on my cable modem logs that I have specific channels with incredibly high uncorrectables (in the tens of millions after a few days) despite a strong SnR (approx 40 on all). Checking my logs, my modem is regularly throwing T3 and T4 errors.

For troubleshooting, I'm in an apartment complex and am limited in what I have access to regarding cable lines. I've tried the other cable jack in my unit, unscrewed the wall plate and plugged straight in, factory reset everything, etc. My cable modem worked fine in a previous building as of July, so I'm fairly confident it is not my hardware. Bonus - I connected to an open CoxWifi in my building that's nearby and found similar packet loss, so it seems building-wide.

Logs are here if anyone has advice: This is from a CM-500 cable modem that I own.

My research indicates that this is likely an issue outside of my control. When I contacted support, they said in summary: "our end looks fine because your SnR is good, so talk to your cable modem manufacturer" and insisted it was my cable modem. Even when I mentioned my modem working fine in other buildings, their response was "your cable modem could be holding onto settings that a factory reset doesn't fix." This cable modem has moved buildings without issue before.

The dilemma - when I asked about a tech, they stated that it would be $75 if they didn't find an issue on their end. I'm a graduate student - buying a new cable modem like it's whatever or losing $75 if they don't acknowledge an issue isn't an easy proposition.

Does anyone have advice on how to most effectively navigate this without potentially spending hundreds?

2 Replies

  • SharonL's avatar
    Former Moderator

    This appears as if you may need someone to investigate your account personally. We would be able to assist you with this. Please reach us on Twitter at @CoxHelp, visit us on Facebook, or email us at Provide us the name on the account with the complete service address with a link to this thread so we can get started. Thank you.

    Cox Support Forum Moderator
  • theperson88's avatar
    New Contributor

    Quick update - went ahead and rented a Panoramic modem. It's using different downstream channels which aren't throwing uncorrectables anymore. However, the upstream channels are the same, and I get an identical amount of packet loss (2% over about 5 minutes, with large spikes to 20-30% periodically). I still have internet hangs where streams, downloads, websites, and meetings completely halt for about 10 seconds a few times an hour. My family in the area uses Cox with 0% packet loss, and my cellphone's internet also has 0% packet loss.

    I will go ahead and contact support - I think I can say for certain that there is an issue on their end. While my downstream uncorrectables seem to be okay now, that seems to be only because I'm on different downstream channels. My upstream channels, being basically the same, likely still have an issue that is leading to the packet loss. Either way, there's an issue somewhere to be fixed.

    Mostly just wanted to post this update if anyone else is troubleshooting out there, and to make a more concise story for when I include this thread when contacting tech support.