M

13 Messages

Tuesday, September 17th, 2024 12:01 AM

Cable Modem Issues - T3 Timeout & Failed to acquire QAM/QPSK symbol timing, Uncorrectable Codeword Errors

I have xfinity gig extra plan. I have a Netgear Nighthawk CM3000 modem, which is brand new. I just replaced a relatively new CM2000 due to these issues, only to find the same thing happening with the new modem. The routers are TP link Decos, but they are fine.

I am having issues with intermittent connectivity, some random restarts, and web pages that don't load fully. There also seems to be some interference issues. I checked the modem logs and sure enough there are an enormous amount of uncorrectable codeword errors in my downstream OFDM channels only. They rack up at an alarming rate of almost one million per hour at times. I also have critical events for T3 timeouts, and SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing, whenever the modem is restarted. 

I want to note that I took the modem down to where the coax line comes in from the street, and attached it there to test it before any splitters, other cables, etc. The power levels went up, but the issues persisted. Thus I suspect the issue is either outside the house, or possibly the single coax line that comes from the outside of my house (ISP entry point) to inside my house. Likely the former.  I will post some diagnostic info below for reference. This was taken just minutes after rebooting. Again, despite power levels rising a bit, all of the issues remained the same when connecting the modem right to the first coax line. Same issues with two modems as well.

Does anyone know what the issue might be? Will I need a tech visit? If so, Xfinity please help!

Cable Diagnostic

Status: Good

Action:
Your setup looks fine. If you can't access the internet, make sure you properly activated the modem. If modem has been activated and you still can't access the internet, contact your service provider for troubleshooting help.
If you can access the internet but has other internet issue, the Netgear Cable Knowledge Base can provide additional troubleshooting info.

CM Status: Good

Downstream Status: Good

    Downstream Power Level: Good

    Downstream SNR Level: Good

Upstream Status: Good

    Upstream Power Level: Good


Current Time: Mon Sep 16 18:36:32 2024

Startup Procedure
Acquire Downstream Channel: 513000000 Hz  Locked
Connectivity State:          OK       Operational
Boot State:                  OK       Operational
Security:                   Enabled   BPI+
IP Provisioning Mode:       Honor MDD   IPv6 only


Downstream Bonded Channels
Channel LockedStatus Modulation ChannelID  Frequency     Power    SNR   Correctables Uncorrectables     
      1     Locked     QAM256     29     513000000 Hz     -5.3     40.1     0     0
      2     Locked     QAM256      9     387000000 Hz     -4.2     41     0     0
      3     Locked     QAM256     10     393000000 Hz     -4.2     40.9     0     0
      4     Locked     QAM256     11     399000000 Hz     -4.8     40.5     0     0
      5     Locked     QAM256     12     405000000 Hz     -4.6     40.5     0     0
      6     Locked     QAM256     13     411000000 Hz     -4.4     40.7     0     0
      7     Locked     QAM256     14     417000000 Hz     -4.4     40.8     0     0
      8     Locked     QAM256     15     423000000 Hz     -4.9     40.5     0     0
      9     Locked     QAM256     16     429000000 Hz     -4.6     40.7     0     0
     10     Locked     QAM256     17     435000000 Hz     -4.5     40.7     0     0
     11     Locked     QAM256     18     441000000 Hz     -4.9     40.4     0     0
     12     Locked     QAM256     19     447000000 Hz     -4.5     40.5     0     0
     13     Locked     QAM256     20     453000000 Hz     -4.6     40.5     0     0
     14     Locked     QAM256     21     459000000 Hz     -4.6     40.4     0     0
     15     Locked     QAM256     22     465000000 Hz     -4.9     40.2     0     0
     16     Locked     QAM256     23     471000000 Hz     -4.6     40.4     0     0
     17     Locked     QAM256     24     477000000 Hz     -4.9     40.2     0     0
     18     Locked     QAM256     25     483000000 Hz     -5.2     40     0     0
     19     Locked     QAM256     26     489000000 Hz     -5.3     40     0     0
     20     Locked     QAM256     27     495000000 Hz     -5.4     39.7     0     0
     21     Locked     QAM256     28     507000000 Hz     -5.6     39.9     0     0
     22     Locked     QAM256     30     519000000 Hz     -5.9     39.6     0     0
     23     Locked     QAM256     31     525000000 Hz     -5.5     39.8     0     0
     24     Locked     QAM256     32     531000000 Hz     -5.4     39.9     0     0
     25     Not Locked     Unknown      0     0 Hz     0.0     0.0     0     0
     26     Not Locked     Unknown      0     0 Hz     0.0     0.0     0     0
     27     Not Locked     Unknown      0     0 Hz     0.0     0.0     0     0
     28     Not Locked     Unknown      0     0 Hz     0.0     0.0     0     0
     29     Not Locked     Unknown      0     0 Hz     0.0     0.0     0     0
     30     Not Locked     Unknown      0     0 Hz     0.0     0.0     0     0
     31     Not Locked     Unknown      0     0 Hz     0.0     0.0     0     0
     32     Not Locked     Unknown      0     0 Hz     0.0     0.0     0     0

Upstream Bonded Channels
Channel   LockedStatus  ChannelType ChannelID   SymbolRate        Frequency       Power     
      1       Locked       ATDMA     47       5120 Ksym/sec       29200000 Hz       48.0 dBmV
      2       Locked       ATDMA     45       5120 Ksym/sec       16300000 Hz       48.8 dBmV
      3       Locked       ATDMA     46       5120 Ksym/sec       22800000 Hz       48.8 dBmV
      4       Locked       ATDMA     48       5120 Ksym/sec       35600000 Hz       47.0 dBmV
      5       Not Locked       Unknown      0       0       0       0.0
      6       Not Locked       Unknown      0       0       0       0.0
      7       Not Locked       Unknown      0       0       0       0.0
      8       Not Locked       Unknown      0       0       0       0.0

Downstream OFDM Channels
Channel   LockedStatus  ProfileID  ChannelID    Frequency       Power       SNR/MER    ActiveSubcarrier    Unerror    Correctable   Uncorrectable
      1     Locked     0 ,1 ,2 ,3      1     537000000 Hz     -5.42 dBmV     37.7 dB     1108 ~ 2987     28760832     25848155     458143
      2     Not Locked     0      0     0 Hz     0 dBmV     0 dB     0 ~ 4095     0     0     0

Upstream OFDMA Channels
Channel   LockedStatus    ProfileID    ChannelID    Frequency       Power
      1     Not Locked     0      0     0 Hz     0 dBmV
      2     Not Locked     0      0     0 Hz     0 dBmV

Event Log
         Time               Priority     Description
Mon Sep 16 18:25:23 2024     Notice (6)     CM-STATUS message sent. Event Type Code: 24; Chan ID: 1; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 2.;
Mon Sep 16 18:23:25 2024     Notice (6)     CM-STATUS message sent. Event Type Code: 16; Chan ID: 1; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 2 3.;
Mon Sep 16 18:21:20 2024     Notice (6)     CM-STATUS message sent. Event Type Code: 16; Chan ID: 1; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 3.;
Mon Sep 16 18:21:03 2024     Notice (6)     DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;
Mon Sep 16 18:20:59 2024     Notice (6)     TLV-11 - unrecognized OID;
Time Not Established     Notice (6)     Honoring MDD; IP provisioning mode = IPv6
Time Not Established     Critical (3)     No Ranging Response received - T3 time-out;
Time Not Established     Critical (3)     SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;; 

thanks!

13 Messages

2 months ago

@Xfinity Support @XfinityRaul can anyone advise if I need a tech visit for these connection issues?

Official Employee

 • 

1.8K Messages

Hey there mikemot21, thank you for taking the time to create such a detailed post and for giving me a chance to work with you on this. Given what you've mentioned, we may need to get a tech visit scheduled, however; I'd like to pull up your account, review those signal levels, and go from there. But if a tech is needed, I can certainly help on that front as well. In order to get started can you please send a direct message to Xfinity Support with your full name and full address by clicking the chat icon in the top right? Here's the detailed steps to direct message us:

• Click "Sign In" if necessary

• Click the "Direct Message” icon (upper right corner of this page)

• Click the "New message" (pencil and paper) icon

• Type "Xfinity Support" in the to line and select "Xfinity Support" from the drop-down list

• Type your message in the text area near the bottom of the window

• Press Enter to send your message

 

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 a reply as the Accepted Answer.tick

Expert

 • 

106.9K Messages

2 months ago

Yes. That would be the next step. 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 up 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.


Good luck !

13 Messages

2 months ago

Update. Tech came out and said it’s a bad line. Readings at their pole were good but readings at the end of line near my house were poor. They are putting a temporary line over my yard for now, and will then be sending people to lay one underground soon.

Official Employee

 • 

1K Messages

mikemot21 Thanks for letting us know what work has been done! The new line will be key to getting great internet service.
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 a reply as the Accepted Answer.tick

13 Messages

So the temp line has been hooked up for over a day. Upstream power decreased , and downstream increased slightly. There are no uncorrectbke code word errors in my modem diagnostics, and connectivity and speeds seem good. 

however, my modem event logs still show that with every reboot, there is at least one t3 timeout and issues with sync to QAM/QPSK. 

any ideas what might be the root cause of this? Is it possibly another connection or interference issue outside of my home? Granted it’s not causing me major issues, but still seems to be something that can and should be corrected. 

Official Employee

 • 

1.8K Messages

 

mikemot21, It's possible that there is an issue further upstream, but we'd need a tech to come out and make that determination. I'd like to review your account to confirm a pending work order to finish up that temporary line. When you get a chance please send a DM using the steps listed above. 

 

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 a reply as the Accepted Answer.tick

13 Messages

Done! I DM xfinity support.

Official Employee

 • 

1K Messages

 

mikemot21 Hey there. We see the DM on our end, and will continue the conversation over there.

 

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 a reply as the Accepted Answer.tick
forum icon

New to the Community?

Start Here