While there is no published information regarding the E 8 error code, some sources suggest that E-8 is a boot up stage error. Your box might be fried and needs a new cable box.
According to Time Warner Cable, error codes that display on the front of the box vary depending on the manufacturer of your Set-Top Box. Examples of error codes you may see are h.000, E01, Fr.00, 8888 and CC99. Most Set-Top Box errors can be resolved by rebooting.
Steps to Reboot Your Set-Top Box:
Please note that the reboot process takes approximately 5 minutes to complete.
Sign in to My Account.
Locate Activate and Troubleshoot Services on the main screen.
Select the Troubleshoot tab.
Select TV from the "Which service are you having an issue with?" dropdown.
If you have more than one Set-Top Box, click the Troubleshoot button for the appropriate device.
Select a symptom from the list.
Select the Reboot My Box button.
Or, to manually reboot:
Turn off the Set-Top Box by either using your remote control or by pressing the POWER button on the box.
Carefully unplug the Set-Top Box power cord from the electrical outlet or power strip if you're using one.
Wait 30 seconds while the Set-Top Box completely shuts off.
Plug the power cord back in. The Set-Top Box will automatically reboot - this may take a few minutes.
Wait for the time or channel to appear on the front of the box or, if your receiver doesn’t have a time/channel display, for the reboot process to show as complete on-screen.
Turn on the TV and Set-Top Box.
If rebooting your Set-Top Box does not clear the error, you may call Time Warner Cable at 1-800-892-4357 and a TWC Care Representative will assist you.