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WorksOnMyMachine
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Friday, February 27th, 2026 4:07 PM

Recurring outages after tech visit – T3/T4 timeouts and upstream power spikes

Hi everyone,

I’m still experiencing intermittent service outages after a recent technician visit. The issue temporarily improved but has returned.

My DOCSIS 3.1 modem logs show repeated T3/T4 timeouts and Dynamic Range Window violations during the outages.

Signal levels currently look like this:

• Downstream: ~0 dBmV, 37–38 dB SNR across channels (looks healthy)
• Upstream transmit power: consistently 46–47+ dBmV and rises prior to outages
• During outages the modem reboots and my router loses its WAN IP

Based on this, it appears to be an upstream noise/ingress issue outside the home rather than an inside wiring problem.

Could this be escalated to maintenance/line technicians to investigate the upstream path and neighborhood plant?

Thank you!

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27 days ago

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EG

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116.9K Messages

29 days ago

You are going to have to have a premises-facing tech visit first. If they can not find or fix a problem at your home, it is they who are the only ones that can escalate it up to their line / network / maintenance dept. techs. It is their S.O.P. to start at the home. And if the problem is found to be anywhere on their side of the demarcation point, there will not be any charge.


Good luck !

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WorksOnMyMachine

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5 Messages

29 days ago

Thanks for the guidance, that makes sense.

I actually did have a premises technician visit recently. After that visit the connection was stable for about a week, but the intermittent outages have now returned.

Since the visit, I’ve continued monitoring the modem signal levels and logs. Here’s what I’m consistently seeing during outages:

• Repeated T3/T4 timeouts
• Dynamic Range Window violations
• Upstream transmit power rising into the 46–47+ dBmV range before service drops
• Modem sometimes fully reboots during the events
• Router loses WAN IP and I cannot reach the modem locally during the outage

Meanwhile the downstream side remains excellent and stable:
• ~0 dBmV power
• 37–38 dB SNR across channels

Because the inside wiring, connectors, and drop were already checked/replaced during the visit, and the downstream levels are clean, this looks increasingly like an intermittent upstream noise/ingress issue outside the home (plant/node).

What would be the best way to get this re-opened and escalated for a line/maintenance investigation? I’m happy to provide logs, timestamps, or schedule another visit if needed.

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EG

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116.9K Messages

@WorksOnMyMachine wrote;

or schedule another visit if needed.

That would be the way to move forward. I'm not certain, but I believe that it may take three failed home visits before it can be referred to their line / plant maintenance department.

I am not a Comcast Employee.
I am a Customer Expert volunteering my time to help other customers here in the Forums.
We ask that you post publicly so people with similar questions may benefit from the conversation.

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29 days ago

WorksOnMyMachine

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28 days ago

Thank you. Tech is on the way and we'll start racking up those failed home visits.

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XfinityThomasB

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2.6K Messages

WorksOnMyMachine Appreciate the heads-up on this! What time was appointment scheduled? 

I am an Official Xfinity Employee.
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27 days ago

WorksOnMyMachine

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Hi Thomas, thanks for jumping in!

The appointment was Friday afternoon (Feb 27).

I wanted to share an update from that visit because the technician uncovered something important on the pole that may be related to the upstream issues I’ve been reporting.

During the visit the tech:
• Replaced the drop from the pole to the house
• Replaced exterior fittings and the ground block/line conditioner
• Replaced worn connectors on the pole that had exposed braid/foil

While working at the pole he also discovered that the tap port feeding my home is currently split and feeding a second neighbor. He indicated this should not be the case and submitted a work order to replace the existing 2-port tap with a 4-port tap so each home has a dedicated connection.

Since this involves outside plant work, I’m unsure how to track that request or when the tap replacement might be scheduled.

Given the ongoing T3/T4 timeouts and high upstream transmit power (46–47+ dBmV), I want to make sure the maintenance/line team work order for the tap replacement is visible and moving forward.

Could you help check the technician notes and confirm the maintenance request is in progress?

Thank you very much for the help!

I'll send my account number privately. 

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27 days ago

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WorksOnMyMachine

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Or maybe I can't send it privately. Account number: [Edited: Personal Information]

(edited)

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27 days ago

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XfinityJustinM

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621 Messages

@WorksOnMyMachine, please keep in mind that you are currently speaking on the public forum. You'll want to wait until we invite you to send us a direct message before sharing personal information that should only be shared with us via direct message. We can check the notes to see if the technician referred the work to maintenance. Just kick things off by sending us a direct message with your full name and service address. 

To send a "Direct Message" to Xfinity Support: 
Click "Sign In" if necessary 
Click the "Direct Messaging" icon 
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

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27 days ago

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