Hello.

I recently downloaded windows defender and it will not update. It says error found: 80004002

What can I do to fix this?

How to troubleshoot definition update issues for Windows Defender.
Microsoft Update Solution Center (includes a list of update issues)
How to troubleshoot common Windows Update, Microsoft Update installation issues
Troubleshooting: Automatic Updates
...Errors when you use Windows Update or Microsoft Update to install updates

You can also check with:
Newsgroups for Windows Defender
Windows Defender Support & Training if all else fails, click the link titled Phone Support