Signal levels have been increasing over several weeks to the point now where all of the channels are our of spec.
Nothing has changed inside my home. There are two splitters in the line. They have been there for over a year and have not been touched since installed.
ANTRONIX®
2-WAY SPLITTER 5-1002MHz CMC2002H-A
-3.5dB OUT
-3.5dB OUT
My owned modem = Netgear Nighthawk CM3000
Firmware = V6.01.04
Cable Diagnostic
Status: Poor
Action: [Downstream Power Level]
CM Status:
Downstream Status:
Upstream Status:
Refresh Save Cable Diagnostic Info
Advanced Information
Frequency Start Value
This field below allows you to modify the frequency the cable modem start with its scan during initialization and registration. Enter the new start frequency and restart the cable modem for it to take effect.
Bandwidth is about 2/3 of what I pay for (1.2 gigs).
There are daily T3 errors in the log:
Event Log Clear Log Refresh Export Time Priority Description
Sat Oct 10 03:10:24 2026 (Critical (3)) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
Time Not Established (Notice (6)) Honoring MDD; IP provisioning mode = IPv6
Time Not Established (Critical (3)) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
Thu Oct 08 21:35:34 2026 (Critical (3)) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
Time Not Established (Critical (3)) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
Fri Sep 18 21:36:26 2026 (Critical (3)) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
Time Not Established (Critical (3)) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
vadeltachi Thanks for reaching out to us about the T3 timeouts, and the speed concern. We can certainly help with troubleshooting this with you here. Since it started has the internet equipment been power cycled, have you used the Xfinity app to do some basic troubleshooting, and what is the speed you get when testing with a device hardwired to the internet device currently?
I am an Official Xfinity Employee. Official Employees are from multiple teams within Xfinity: CARE, Product, Leadership. We ask that you post publicly so people with similar questions may benefit from the conversation. Was your question answered? Please mark as Best Answer.
Everything is power cycled daily (modem first and then router).
This has not solved the issues.
The app is not suited for customer-owned equipment and failed in a do-loop asking which device is having issues. All of the devices are having issues as the issue is a signal that is clearly too high, but not detected by the app. The T3 errors were not detected by the app.
Bandwidth routinely caps at 650 mbps and was previously between 1.2 and 1.4. The router runs the speed test from itself to the modem.
I am an Official Xfinity Employee. Official Employees are from multiple teams within Xfinity: CARE, Product, Leadership. We ask that you post publicly so people with similar questions may benefit from the conversation. Was your question answered? Please mark as Best Answer.
Please circle back here and post any possible solutions for the issue here in these open public forums so that all readers here may benefit from the exchange / info. This is in keeping with the spirit for which these public help forums were originally intended. Thank you.
EG
Expert
•
122K Messages
2 days ago
First. Are you actually experiencing any connection/droput problems ?
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EG
Expert
•
122K Messages
2 hours ago
@vadeltachi @XfinityAngie
Please circle back here and post any possible solutions for the issue here in these open public forums so that all readers here may benefit from the exchange / info. This is in keeping with the spirit for which these public help forums were originally intended. Thank you.
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