Bingo!

Since yesterday i keep getting this error.

Any ideas how to fix this?

See this post for info on the problem.

Error Codet install - Microsoft Community

In the past I had Defender not update a couple times. I solved it by d/l ing the definitions manually & installing them. In both instances after doing this, my updates started working again.

You may also wish to run a SFC to see if anything need repaired.

FIX: I was able to fix this by opening CMD as Admin and typing (with quotes):


"%PROGRAMFILES%Windows DefenderMPCMDRUN.exe" -RemoveDefinitions -All


Then I typed (with quotes:


"%PROGRAMFILES%Windows DefenderMPCMDRUN.exe" -SignatureUpdate


Hope this helped!

FIX: I was able to fix this by opening CMD as Admin and typing (with quotes):


"%PROGRAMFILES%Windows DefenderMPCMDRUN.exe" -RemoveDefinitions -All


Then I typed (with quotes:


"%PROGRAMFILES%Windows DefenderMPCMDRUN.exe" -SignatureUpdate


Hope this helped!

This worked like a charm. Thank you.

I've been chasing that one all day !

FIX: I was able to fix this by opening CMD as Admin and typing (with quotes):


"%PROGRAMFILES%Windows DefenderMPCMDRUN.exe" -RemoveDefinitions -All


Then I typed (with quotes:


"%PROGRAMFILES%Windows DefenderMPCMDRUN.exe" -SignatureUpdate


Hope this helped!

Yes. This actually works, thanks a lot.

Doesn't work!

FIX: I was able to fix this by opening CMD as Admin and typing (with quotes):


"%PROGRAMFILES%Windows DefenderMPCMDRUN.exe" -RemoveDefinitions -All


Then I typed (with quotes:


"%PROGRAMFILES%Windows DefenderMPCMDRUN.exe" -SignatureUpdate


Hope this helped!

Helped me out
The update still showed in Windows Update but hitting retry cleared it.

I have posted the fix on many Microsoft blog but all have been deleted. Why would they delete the fix ?

Worrying

I had this problem on a Win 10 Home based computer. Cannot disable Defender.

Deleted all files in C:WindowsSoftwareDistributionDownload, and retried update, but the problem were still there. Clicked on Try Again, and Voila!