CM-01
Xfinity ISP
Severity: CriticalWhat Does This Error Mean?
Xfinity CM-01 is a cable modem startup error meaning the modem failed to complete its registration process with Xfinity's network. During startup, a cable modem goes through several steps to connect: scanning channels, locking on, downloading configuration, and registering. CM-01 means one of those steps failed and the modem gave up. You will have no internet until this is resolved.
Affected Models
- Xfinity-provided cable modems
- Xfinity XB6 gateway
- Xfinity XB7 gateway
- Xfinity XB8 gateway
- Approved third-party DOCSIS modems on the Xfinity network
Common Causes
- The coax cable signal is too weak for the modem to complete the registration process
- The modem is not provisioned (recognized) on Xfinity's network — especially after account changes
- A damaged or corroded coax cable or connector is degrading the signal
- Xfinity is experiencing a network outage in your area
- The modem's firmware is outdated or corrupted and cannot complete the startup sequence
How to Fix It
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Unplug the modem's power cord. Wait 60 seconds. Plug it back in. Watch the modem lights cycle through startup — this takes 2–5 minutes on average.
A power cycle forces a fresh registration attempt, which clears most CM-01 errors.
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Check the coax cable connection on the back of the modem. Hand-tighten it. Also check the wall outlet end of the coax cable.
A slightly loose coax connector reduces signal and can prevent modem registration.
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Remove any splitters between the wall and the modem. Connect the modem directly to the coax wall outlet.
Splitters weaken the signal. Bypassing them gives the modem the best chance of completing registration.
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Check Xfinity's status page at xfinity.com/support/status or open the Xfinity app and check for active outages in your area.
An area outage will cause CM-01 across all modems on the affected node — nothing you do will fix it until Xfinity resolves the outage.
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If you are using your own modem (not an Xfinity-rented one), verify it is on Xfinity's approved modem list at xfinity.com/support/articles/list-of-approved-modems. An unapproved modem will never register successfully.
Xfinity updates their approved modem list. Older or uncertified modems get blocked when the network upgrades.
When to Call a Professional
CM-01 that persists after a reboot and cable check requires Xfinity support. Call 1-800-XFINITY and tell them you see CM-01 on your modem. They can check your signal levels remotely and attempt to re-provision your modem. If the signal is the issue, they will send a technician at no additional cost for Xfinity-rented equipment.
Frequently Asked Questions
How long should I wait for the modem to come back online after seeing CM-01?
Give it at least 5 minutes after the power cycle. The full startup and registration process can take 3–5 minutes on a working connection. If the CM-01 error persists after 10 minutes, the modem is genuinely stuck and you need to call Xfinity.
My new Xfinity modem shows CM-01. Is it defective?
Not necessarily. A brand-new modem needs to be provisioned on Xfinity's network before it will work. If you set up the modem yourself without going through Xfinity's activation process, call Xfinity and provide your modem's MAC address (printed on the label on the bottom). They will add it to your account, and the modem should come online within minutes.
Can CM-01 be caused by interference from another device?
Yes. Electrical interference from devices near the modem or on the same coax line can degrade signal quality. Try moving the modem away from large electronics like televisions, amplifiers, or cable boxes. Also check that all unused coax outlets in your home are capped — open coax outlets can introduce noise into the line.