SYNC Timing Synchronization failure | UCD invalid or channel unusable

Internet cuts out at least once each day, usually about 3:45PM central time. Modem reboot doesn't typically solve the problem although as soon as an appointment is booked, we receive a message a short while later that the problem was fixed on xfinity's side and sure enough everything is working again. Techs came out and replaced the cable to the house from the box twice. Neighbors internet remains up and running so it appears we are the only ones affected. We've replaced the modem with a Netgear CM1100. Logs look like:

Time	Priority	Description
2023-09-12, 14:47:33	Critical (3)	UCD invalid or channel unusable;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
2023-09-12, 14:47:32	Notice (6)	DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
2023-09-12, 14:47:18	Notice (6)	Honoring MDD; IP provisioning mode = IPv6
2023-09-12, 14:47:14	Critical (3)	UCD invalid or channel unusable;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Time Not Established	Notice (6)	Honoring MDD; IP provisioning mode = IPv6
2023-09-12, 14:37:55	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2023-09-12, 14:37:50	Critical (3)	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
2023-09-12, 14:37:47	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
2023-09-12, 14:37:46	Critical (3)	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
2023-09-12, 14:37:06	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
2023-09-12, 14:37:02	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:40:43	Critical (3)	UCD invalid or channel unusable;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:40:29	Critical (3)	UCD invalid or channel unusable;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:38:53	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:38:43	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:38:33	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:38:23	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:38:13	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:38:03	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:37:53	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:37:43	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:37:24	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:37:14	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:37:06	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:36:51	Critical (3)	Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:36:27	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:35:43	Critical (3)	Unicast Ranging Received Abort Response - Re-initializing MAC;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:35:25	Critical (3)	UCD invalid or channel unusable;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:34:12	Critical (3)	No Ranging Response received - T3 time-out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:32:38	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:32:28	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:32:18	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:32:08	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:31:58	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:31:48	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:31:38	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:31:26	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:31:06	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:30:56	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2023-09-09, 21:30:04	Critical (3)	No Ranging Response received - T3 time-out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;

Responses

EG

Expert

•

111.8K Messages

2 years ago

Please also copy all of the text in its entirety of the *Downstream Power Levels*, the *SNR's* (Signal to Noise Ratios), and the *Upstream Power Level* numbers and paste them into your next post.

2

0

U

user_d14d33

2 Messages

<tabindex=-1>Downstream Bonded Channels</tabindex=-1>

Channel	Lock Status	Modulation	Channel ID	Frequency	Power	SNR / MER	Unerrored Codewords	Correctable Codewords	Uncorrectable Codewords
1	Locked	QAM256	28	591000000 Hz	-6.8 dBmV	39.9 dB	163063252	0	0
2	Locked	QAM256	1	429000000 Hz	-2.5 dBmV	41.6 dB	162146661	0	0
3	Locked	QAM256	2	435000000 Hz	-2.6 dBmV	41.5 dB	162135768	0	0
4	Locked	QAM256	3	441000000 Hz	-2.3 dBmV	41.7 dB	162137794	0	0
5	Locked	QAM256	4	447000000 Hz	-1.5 dBmV	42.1 dB	162157057	0	0
6	Locked	QAM256	5	453000000 Hz	-1.3 dBmV	42.4 dB	162160246	0	0
7	Locked	QAM256	6	459000000 Hz	-1.4 dBmV	42.4 dB	162164358	0	0
8	Locked	QAM256	7	465000000 Hz	-1.3 dBmV	42.4 dB	162168214	0	0
9	Locked	QAM256	8	471000000 Hz	-1.7 dBmV	42.2 dB	162171887	0	0
10	Locked	QAM256	9	477000000 Hz	-2.4 dBmV	41.9 dB	162175737	0	0
11	Locked	QAM256	10	483000000 Hz	-3.1 dBmV	41.4 dB	162179864	0	0
12	Locked	QAM256	11	489000000 Hz	-2.9 dBmV	41.6 dB	162183436	0	0
13	Locked	QAM256	12	495000000 Hz	-3.1 dBmV	41.5 dB	162187164	0	0
14	Locked	QAM256	13	501000000 Hz	-3.3 dBmV	41.6 dB	162191079	0	0
15	Locked	QAM256	14	507000000 Hz	-2.7 dBmV	41.9 dB	162194436	0	0
16	Locked	QAM256	15	513000000 Hz	-2.6 dBmV	42.0 dB	162199358	0	0
17	Locked	QAM256	16	519000000 Hz	-3.2 dBmV	41.8 dB	162203039	0	0
18	Locked	QAM256	17	525000000 Hz	-3.6 dBmV	41.6 dB	162206678	0	0
19	Locked	QAM256	18	531000000 Hz	-3.9 dBmV	41.5 dB	162210659	0	0
20	Locked	QAM256	19	537000000 Hz	-4.5 dBmV	41.0 dB	162213732	0	0
21	Locked	QAM256	20	543000000 Hz	-5.1 dBmV	40.8 dB	162217886	0	0
22	Locked	QAM256	21	549000000 Hz	-5.2 dBmV	37.6 dB	162221178	0	0
23	Locked	QAM256	22	555000000 Hz	-5.3 dBmV	38.4 dB	162225285	0	0
24	Locked	QAM256	23	561000000 Hz	-5.3 dBmV	40.8 dB	162228621	0	0
25	Locked	QAM256	24	567000000 Hz	-5.4 dBmV	40.8 dB	162232674	0	0
26	Locked	QAM256	25	573000000 Hz	-6.0 dBmV	40.5 dB	162236549	0	0
27	Locked	QAM256	26	579000000 Hz	-6.0 dBmV	40.4 dB	162241009	0	0
28	Locked	QAM256	27	585000000 Hz	-6.4 dBmV	40.2 dB	162244515	0	0
29	Locked	QAM256	29	597000000 Hz	-6.5 dBmV	40.1 dB	162248336	0	0
30	Locked	QAM256	30	603000000 Hz	-6.2 dBmV	39.9 dB	162252307	0	0
31	Locked	QAM256	31	609000000 Hz	-6.2 dBmV	40.2 dB	162268864	0	0
32	Locked	QAM256	32	615000000 Hz	-6.1 dBmV	40.4 dB	162257796	0	0

<tabindex=-1>Upstream Bonded Channels</tabindex=-1>

Channel	Lock Status	Modulation	Channel ID	Frequency	Power
1	Locked	ATDMA	1	16400000 Hz	51.0 dBmV
2	Locked	ATDMA	2	22800000 Hz	50.5 dBmV
3	Locked	ATDMA	3	29200000 Hz	51.0 dBmV
4	Locked	ATDMA	4	35600000 Hz	51.0 dBmV
5	Not Locked	Unknown	0	0 Hz	0.0 dBmV
6	Not Locked	Unknown	0	0 Hz	0.0 dBmV
7	Not Locked	Unknown	0	0 Hz	0.0 dBmV
8	Not Locked	Unknown	0	0 Hz	0.0 dBmV

<tabindex=-1>Downstream OFDM Channels</tabindex=-1>

Channel	Lock Status	Modulation / Profile ID	Channel ID	Frequency	Power	SNR / MER	Active Subcarrier Number Range	Unerrored Codewords	Correctable Codewords	Uncorrectable Codewords
1	Locked	0, 1, 2, 3	193	957000000 Hz	-8.8 dBmV	35.8 dB	148 ~ 3947	13746793	8795325	0
2	Not Locked	0	0	0 Hz	-0.4 dBmV	0.0 dB	0 ~ 4095	0	0	0

<tabindex=-1>Upstream OFDMA Channels</tabindex=-1>

Channel	Lock Status	Modulation / Profile ID	Channel ID	Frequency	Power
1	Not Locked	Unknown	0	0 Hz	0 dBmV
2	Not Locked	Unknown	0	0 Hz	0 dBmV

2 years ago

0

XfinityMichaelC

Administrator

•

4.4K Messages

Thank you for providing that information, @user_d14d33! Having a look into the modem, everything is looking good there other than the upstream being slightly out of specification as @EG had mentioned. He was also heading in the right direction for checking for splitters as they do have a tendency to go bad. Please let us know if you are still having issues so we can try to get to the bottom of it.

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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

EG

Expert

•

111.8K Messages

2 years ago

The upstream power is too high and it may be intermittently fluctuating even higher to out of spec levels. The downstream power is on the low / weak side as well. That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, latency problems, and the un-bonding of channels.

In an effort to try to obtain better connectivity / more wiggle room, check to see if there are any excess/unneeded coax cable splitters in the line leading to the modem that can be eliminated/re-configured. Any splitters that remain should be high quality and cable rated for 5-1002 MHz, bi-directional, and no gold colored garbage from Home Depot, Target, Wal-Mart, etc. Splitters should be swapped with known to be good / new ones to test.

Also check the coax cable for any damage such as cuts, nicks, abrasions, kinks, sharp bends, etc.

If there aren't any unneeded splitters that can be eliminated and if your coax wiring setup can't be reconfigured so that there is a single two-way splitter connected directly off of the drop from the street / pole with one port feeding the modem and the other port feeding the rest of the house/equipment with additional splits as needed and you've checked all the wiring and fittings for integrity and tightness and refresh them by taking them apart then check for and clean off any corrosion / oxidation on the center wire and put them back together again, then perhaps it's best to book a tech visit to investigate and correct.

Good luck with it !

0

Your Home Network

user_d14d33

SYNC Timing Synchronization failure | UCD invalid or channel unusable

EG

user_d14d33

XfinityMichaelC

EG

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