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user_2199e8
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Monday, November 21st, 2022 3:28 PM

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SYNC Timing Synchronization failure

My router keeps dropping internet due to SYNC failure.

I have read the other forums and completed the following:

1) Power down/Power up

2) Disconnect everything from network, then power cycle

3) Log into modem and router and manually rebooted

4) Used Xfinity website to force restart from your end 

5) Inspected cable (no splitters, all installed by your tech 1 year ago)

I am out of DIY solutions.

Time Not Established   Critical (3)  

SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing
19:50:20
Sat Nov 19 2022		   Critical (3)   SYNC Timing Synchronization failure - Loss of Sync
Downstream Bonded Channels  
  
   Channel Lock Status Modulation Channel ID Freq. (MHz) Pwr (dBmV) SNR (dB) Corrected Uncorrected
   1 Locked QAM256 20 555.0 4.1 40.3 0 0
   2 Locked QAM256 17 537.0 3.6 40.3 0 0
   3 Locked QAM256 18 543.0 3.7 40.1 0 0
   4 Locked QAM256 19 549.0 3.9 40.3 0 0
   5 Locked QAM256 21 561.0 4.3 40.3 0 0
   6 Locked QAM256 22 567.0 4.4 40.3 0 0
   7 Locked QAM256 23 573.0 4.3 40.2 0 0
   8 Locked QAM256 24 579.0 4.2 40.3 0 0
   9 Locked QAM256 25 585.0 4.4 40.1 0 0
   10 Locked QAM256 26 591.0 4.3 40.3 0 0
   11 Locked QAM256 27 597.0 4.2 39.9 0 0
   12 Locked QAM256 28 603.0 4.1 40.1 0 0
   13 Locked QAM256 29 609.0 4.0 39.9 0 0
   14 Locked QAM256 30 615.0 3.7 39.8 0 0
   15 Locked QAM256 31 621.0 3.8 40.0 0 0
   16 Locked QAM256 32 627.0 3.8 40.0 0 0
   17 Locked QAM256 33 633.0 4.0 40.3 0 0
   18 Locked QAM256 34 639.0 3.1 39.7 0 0
   19 Locked QAM256 35 645.0 4.0 40.2 0 0
   20 Locked QAM256 36 651.0 3.9 40.1 0 0
   21 Locked QAM256 37 657.0 3.8 39.9 0 0
   22 Locked QAM256 38 663.0 3.8 40.0 0 0
   23 Locked QAM256 39 669.0 3.8 40.0 0 0
   24 Locked QAM256 40 675.0 3.7 39.5 0 0
   25 Locked QAM256 41 681.0 3.8 40.0 0 0
   26 Locked QAM256 42 687.0 3.7 39.9 0 0
   27 Locked QAM256 43 693.0 3.8 40.0 0 0
   28 Locked QAM256 44 699.0 3.7 39.9 0 0
   29 Locked QAM256 45 705.0 3.4 39.8 0 0
   30 Locked QAM256 46 711.0 3.3 39.9 0 0
   31 Locked QAM256 47 717.0 3.6 40.1 0 0
   32 Locked OFDM PLC 48 805.0 3.0 39.5 186375444 0
Upstream Bonded Channels  
  
   Channel Lock Status Channel Type Channel ID Symb. Rate (Ksym/sec) Freq. (MHz) Pwr (dBmV)
   1 Locked SC-QAM 73 5120 16.4 39.3
   2 Locked SC-QAM 74 5120 22.8 39.3
   3 Locked SC-QAM 75 5120 29.2 39.5
   4 Locked SC-QAM 76 5120 35.6 39.5

Question

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Updated 

2 years ago

7.9K

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0

EG

Expert

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110K Messages

2 years ago

The signal stats were good / within spec at that snapshot in time. Please post those modem's RF error log entries in their entirety (copy and paste all of the text) but redact the CM and the CMTS MAC addresses for your privacy or else the forum bot will not allow your post to be seen publically.

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user_85935e

Visitor

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5 Messages

2 years ago

I've been having the same issues. Here is my event log @EG 

I am not sure if this is a red herring or not but I have noticed that my internet seems to struggle most often when I assume more people are at home using their Comcast service. I work from home and most weeks there are no issues. However, it recently snowed in my area and my assumption is more people are working from home.

Modem = Motorola MB8611

Event Log
Time  Priority  Description 
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
14:33:12
Thu Aug 25 2022		 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;
20:04:50
Thu Aug 25 2022		 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;
15:43:49
Sat Aug 27 2022		 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
10:21:18
Fri Oct 14 2022		 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
10:03:59
Thu Oct 20 2022		 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
14:06:15
Mon Nov 14 2022		 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
01:12:43
Wed Nov 16 2022		 Critical (3) No Ranging Response received - T3 time-out;
01:12:46
Wed Nov 16 2022		 Critical (3) SYNC Timing Synchronization failure - Failed to receive MAC SYNC frame within time-out period;
01:12:55
Wed Nov 16 2022		 Critical (3) No Maintenance Broadcasts for Ranging opportunities received - T2 time-out;
01:13:26
Wed Nov 16 2022		 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
01:13:41
Wed Nov 16 2022		 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
01:13:41
Wed Nov 16 2022		 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
01:17:17
Wed Nov 16 2022		 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
01:17:50
Wed Nov 16 2022		 Critical (3) SYNC Timing Synchronization failure - Loss of Sync;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
11:38:35
Sat Nov 19 2022		 Critical (3) SYNC Timing Synchronization failure - Loss of Sync;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
Time Not Established Critical (3) DHCP failed - RS sent, no RA received;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
03:31:51
Wed Nov 23 2022		 Critical (3) SYNC Timing Synchronization failure - Loss of Sync;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
09:05:09
Wed Nov 23 2022		 Critical (3) SYNC Timing Synchronization failure - Loss of Sync;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
11:25:09
Thu Dec 1 2022		 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;
Time Not Established Notice (6) Honoring MDD; IP provisioning mode = IPv6
12:29:44
Thu Dec 1 2022		 Notice (6) DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;
12:30:15
Thu Dec 1 2022		 Notice (6) CM-STATUS message sent. Event Type Code: 24; Chan ID: 193; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 0.;
Startup Sequence
   Startup Step Status Comment
   Acquire Downstream Channel 543000000 Hz Locked
   Upstream Connection OK Operational
   Boot State OK Operational
   Configuration File OK
   Security Enabled BPI+


Connection Status
   System Up Time 0 days 00h:04m:23s
   Network Access Allowed


Downstream Bonded Channels
   Channel Lock Status Modulation Channel ID Freq. (MHz) Pwr (dBmV) SNR (dB) Corrected Uncorrected
   1 Locked QAM256 20 543.0 8.3 44.6 0 0
   2 Locked QAM256 13 489.0 8.1 45.1 0 0
   3 Locked QAM256 14 495.0 8.1 45.1 0 0
   4 Locked QAM256 15 507.0 7.6 45.0 0 0
   5 Locked QAM256 16 513.0 7.7 44.9 0 0
   6 Locked QAM256 17 519.0 7.8 45.1 0 0
   7 Locked QAM256 18 525.0 7.8 42.2 0 0
   8 Locked QAM256 19 531.0 8.0 43.8 0 0
   9 Locked QAM256 21 549.0 8.3 45.1 0 0
   10 Locked QAM256 22 555.0 8.4 45.1 0 0
   11 Locked QAM256 23 561.0 8.4 45.0 0 0
   12 Locked QAM256 24 567.0 8.4 42.7 0 0
   13 Locked QAM256 25 573.0 8.3 42.9 0 0
   14 Locked QAM256 26 579.0 8.2 44.7 0 0
   15 Locked QAM256 27 585.0 8.3 44.9 0 0
   16 Locked QAM256 28 591.0 8.5 45.0 0 0
   17 Locked QAM256 29 597.0 8.5 44.9 0 0
   18 Locked QAM256 30 603.0 8.7 44.4 0 0
   19 Locked QAM256 31 609.0 8.8 44.9 0 0
   20 Locked QAM256 32 615.0 8.9 45.0 0 0
   21 Locked QAM256 33 621.0 9.1 45.1 0 0
   22 Locked QAM256 34 627.0 9.1 44.9 0 0
   23 Locked QAM256 35 633.0 9.3 45.0 0 0
   24 Locked QAM256 36 639.0 9.3 44.8 0 0
   25 Locked QAM256 37 645.0 9.4 44.9 0 0
   26 Locked QAM256 38 651.0 9.4 44.9 0 0
   27 Locked QAM256 39 657.0 9.3 45.0 0 0
   28 Locked QAM256 40 663.0 9.3 45.1 0 0
   29 Locked QAM256 41 669.0 9.5 45.1 0 0
   30 Locked QAM256 42 675.0 9.5 44.3 0 0
   31 Locked QAM256 43 681.0 9.2 45.0 0 0
   32 Locked QAM256 44 687.0 8.9 44.4 0 0
   33 Locked OFDM PLC 193 722.0 7.4 43.4 1264344 0


Upstream Bonded Channels
   Channel Lock Status Channel Type Channel ID Symb. Rate (Ksym/sec) Freq. (MHz) Pwr (dBmV)
   1 Locked SC-QAM 1 5120 16.4 45.3
   2 Locked SC-QAM 2 5120 22.8 45.3
   3 Locked SC-QAM 3 5120 29.2 45.0
   4 Locked SC-QAM 4 5120 35.6 44.5
   5 Locked SC-QAM 5 2560 40.4 47.0
   6 Locked SC-QAM 6 2560 10.4 45.5

(edited)

1

0

XfinityRay

Official Employee

 • 

2.7K Messages

Greetings, @user_2199e8 and thread. Have you been able to gather the error logs @EG was requesting or do you need additional assistance?

 

Thank you for sharing your modem logs, @user_85935e. I do not like the look of all of those timeouts! Is the issue only worse when the weather is bad and then improves again or just when you would think more people are at home? Do you have any splitters between the wall outlet and your 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 a reply as the Accepted Answer.tick

2 years ago

0

user_9ea1f1

Visitor

 • 

9 Messages

2 years ago

Same issue here, and Comcast won't do anything.  This has been happening for months, and Comcast refuses to do anything.  My modem disconnects multiple times per day every day.


And comcast has the audacity to expect me to pay full price for this service?  And they wonder why I keep lowering my service?  I refuse to pay top dollar for [Edit: Language] service.  And since there is no other internet provider, I'm [Edit: Language].  So I'll take $50/month and run with it until comcast wants to do their job so I can get better service and ultimately spend more money which you would think is something they would want.

Guess not.

SYNC Timing Synchronization failure - Loss of Sy 01/22/2023 08:10:32 PM Critical
SYNC Timing Synchronization failure - Loss of Sync 01/22/2023 02:46:31 PM Critical
SYNC Timing Synchronization failure - Loss of Sync 01/22/2023 02:25:19 PM Critical
ti_dhcp6c: 72001011-DHCPv6 - Missing Required Option 24 01/21/2023 06:34:33 PM Critical
ti_dhcp6c: 72001011-DHCPv6 - Missing Required Option 82 01/21/2023 06:34:33 PM Critical
ti_dhcp6c: 72001011-DHCPv6 - Missing Required Option 82 01/21/2023 06:34:22 PM Critical
ti_dhcp6c: 72001009-DHCPv6 - No Advertise or Reply Received 1 times 01/21/2023 06:34:22 PM Critical

(edited)

2

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XfinityJohnG

Official Employee

 • 

1.6K Messages

Thank you very much for reaching out to us here @user_9ea1f1. I would be happy to look into any internet servic issue from here for you. Could you send me a direct message with the full name and complete address for your service? 

To send a direct message [private message]:

   Click the "Direct Message" icon or  https://forums.xfinity.com/direct-messaging

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

   The "To:" line prompts you to "Type the name of a person". Instead, type "Xfinity Support" there.

   - As you are typing a drop-down list appears. Select "Xfinity Support" from that list.

   - An "Xfinity Support" graphic replaces the "To:" line.

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

   Press Enter to send it

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

2 years ago

0

user_0b365d

Visitor

 • 

1 Message

Is there a resolution to this issue? I am having the exact same issue of multiple internet disconnects a day and my routers event log is the same as the one above.

2 years ago

0

EG

Expert

 • 

110K Messages

2 years ago

@user_0b365d 

Please create a new topic of your own here on this board detailing your issue. Thanks. The original poster has not returned. 3-month-old dead thread is now being closed.


For future reference, it is better to submit your own post as it creates a ticket to get help, and posting on an old thread can delay getting help.

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