Sync timing synchronization failure

I have a Motorola Modem MB 7621. In the last few months, the cable and internet zaps out for about 2 seconds, multiple times a day. When I went into the modem event log there are dozens of sync timing synchronization failure items listed. Is this due to the age of the modem or something else?

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EG

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14 hours ago

Please post those error log entries in their entirety (copy and paste them, don't post a screenshot) but redact any CM MAC and the CMTS MAC addresses for your privacy. They are considered to be personal information. The posting of personally identifying information is a violation of their forum guidelines. The forum bot will not allow your post to be seen publicly.

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.

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ASPENREX

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@EG

Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MACe;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=e;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=0;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=e;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=00:40:36:67:c0:3e;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=00:;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Thu Jun 19 17:39:14 2025	Critical (3)	Resetting the cable modem due to docsDevResetNow
Time Not Established	Notice (6)	Honoring MDD; IP provisioning mode = IPv6

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13 hours ago

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ASPENREX

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7 Messages

Connection

Startup Sequence

Startup Step	Status	Comment
Acquire Downstream Channel	447000000 Hz	Locked
Upstream Connection	OK	Operational
Boot State	OK	Operational
Configuration File	OK
Security	Enabled	BPI+

Connection Status

System Up Time	5 days 17h:16m:09s
Network Access	Allowed

Downstream Bonded Channels

Channel	Lock Status	Modulation	Channel ID	Freq. (MHz)	Pwr (dBmV)	SNR (dB)	Corrected	Uncorrected
1	Locked	QAM256	4	447.0	-5.8	41.6	133	0
2	Locked	QAM256	1	429.0	-5.7	41.7	263	0
3	Locked	QAM256	2	435.0	-5.8	41.6	196	0
4	Locked	QAM256	3	441.0	-5.8	41.6	238	0
5	Locked	QAM256	5	453.0	-5.7	41.5	79	0
6	Locked	QAM256	6	459.0	-5.7	41.4	90	0
7	Locked	QAM256	7	465.0	-5.7	41.4	122	0
8	Locked	QAM256	8	471.0	-5.4	40.2	149	0
9	Locked	QAM256	9	477.0	-5.5	41.6	117	0
10	Locked	QAM256	10	483.0	-5.6	41.5	96	0
11	Locked	QAM256	11	489.0	-5.4	41.8	111	0
12	Locked	QAM256	12	495.0	-5.6	41.6	87	0
13	Locked	QAM256	13	501.0	-5.9	41.3	162	0
14	Locked	QAM256	14	507.0	-6.0	36.0	186	0
15	Locked	QAM256	15	513.0	-5.9	41.3	113	0
16	Locked	QAM256	16	519.0	-5.8	41.3	137	0
17	Locked	QAM256	17	525.0	-5.6	42.9	78	0
18	Locked	QAM256	18	531.0	-5.4	43.0	127	0
19	Locked	QAM256	19	537.0	-5.3	43.0	169	0
20	Locked	QAM256	20	543.0	-5.5	42.8	113	0
21	Locked	QAM256	21	549.0	-5.1	43.3	116	0
22	Locked	QAM256	22	555.0	-5.1	43.3	102	0
23	Locked	QAM256	23	561.0	-5.2	43.2	223	0
24	Locked	QAM256	24	567.0	-5.2	43.1	181	0
Total							3388	0

Upstream Bonded Channels

Channel	Lock Status	Channel Type	Channel ID	Symb. Rate (Ksym/sec)	Freq. (MHz)	Pwr (dBmV)
1	Locked	ATDMA	1	5120	16.4	43.3
2	Locked	ATDMA	2	5120	22.8	42.5
3	Locked	ATDMA	3	5120	29.2	43.5
4	Locked	ATDMA	4	5120	35.6	43.2
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 Frequency Setting

Downstream Frequency Select

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13 hours ago

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EG

Expert

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111.3K Messages

12 hours ago

This may or may not be the root cause of the problem (YMMV), but it should be addressed regardless. First.

The upstream power is good, but the downstream power is on the low / weak side and it may be intermittently fluctuating even lower to out of spec levels. That can cause random disconnects, spontaneous rebooting of the modem, speed, packet loss, latency problems, and the unbonding 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/reconfigured. 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, animal chews.

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 !

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ASPENREX

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7 Messages

Much appreciated! So the age of the Motorola modem is not related?

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10 hours ago

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EG

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111.3K Messages

10 hours ago

Quite welcome ! Maybe yes, maybe no. The only way to tell for sure is a swap out for another. It's still on their supported devices list.

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Sync timing synchronization failure

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