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Forum Discussion
CM1150 critical errors requiring reboot
I've been using a CM1150V modem with Xfinity for about 18 months w/o issues (replaced an old Arris when it failed). When issues occur (randomly, several time per day) I'll initially noticed internet lagging, then ultimately failing completely and requiring a modem reboot. In the event log, I consistently see Critical(3) errors related to "Started Unicast Maintenance Ranging - No Response received - T3 time-out" and "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing". After googling things a bit, I've reviewed up and down power levels and haven't found anything out of range. I had an Xfinity tech come out and some cables were replaced, and since we now use the Xfinity Stream app in multiple rooms that used to have physical cable boxes, we removed several splitters and an amplifier. My current setup has only one splitter after the line from the pole reaches the house, with one line going to the single remaining cable box (dvr), and the other going to the modem. The Xfinity tech on site was not able to find any signal issues, and multiple calls with 2nd line Xfinity tech support resulted in them claiming they have run multiple diagnostics showing no sign of a signal issue on their end.
To continue troubleshooting this, I picked up an Xfinity Gateway (XB7) from the Xfinity Store, and I've activated that in place of my CM1150V. After switching it over to Bridge Mode, it has been up and running w/o issue for 24 hours now. Does this prove any of the following:
- My CM1150V is defective/broken and needs to be replaced
- The XB7 is more "forgiving" of the signal issues I was encountering or simply handles background restarts to address those issues more cleanly
- Other?
While my CM1150V is out of warranty, it is still covered by Amex extended warranty policy, so I can submit a claim and purchase a new modem (I don't want to continue paying Xfinity $14 per month forever). My concern is that there is still a line issue, and even a new modem will still encounter issues.
Thanks in advance for any insight you can provide!
Jeff
5 Replies
Please post a copy and paste of the modems connection status page.
Be sure your using a good quality LAN cable between the modem and router. CAT6 is recommended.
What is the brand and model of the host wifi router connected to the modem?
Have the ISP check the signal and line quality UP to the modem. Be sure the ISP provisions the modem correctly.
Be sure there are no coax cable line splitters in the between the modem and ISP service box.
Be sure your using good quality RG6 coax cable up to the modem.
Be sure to power OFF the modem for 1 minute then back ON.
https://community.netgear.com/t5/Cable-Modems-Routers/General-info-and-Troubleshooting-for-Cable-Modems/m-p/1530376#M12853
https://kb.netgear.com/24311/Power-level-guidelines-for-a-NETGEAR-cable-modem-router?article=24311
https://www.duckware.com/tech/solving-intermittent-cable-modem-issues.html
https://highspeed.tips/docsis-events/Thanks for the quick response. Unfortunately, since I needed to activate the rented XB7 Gateway from Xfinity temporarily in order to work from home effectively, I can't provide new or updated logs from the CM1150V at the moment (I may be able to reactivate it and monitor things further over the weekend).
My real question is this - is it possible that the XB7 handles signal and line issues more "forgivingly" than CM1150V since, with the exact same setup other than the modem swapout, I don't seem to be encountering the same issues?
Thanks again!
Jeff
Anything is possible. However hard to tell anything with out seeing event and cable connection status logs.
