In order to do that please post the exact model of your system.

Welcome to the Dell Community  @bluelemon 

A reference guide to the XPS Notebook Diagnostic Indicators:

https://www.dell.com/support/article/us/en/19/sln309624/a-reference-guide-to-the-xps-notebook-diagnostic-indicators?lang=en#2014_Present

Hold down the " D " key and power-on.

Does it run the LCD Built-in Self-Test (BIST)

How to Run the LCD Built-in Self-Test on a Dell Laphttps://www.dell.com/support/article/us/en/19/sln131497/how-to-run-the-lcd-built-in-self-test-on-a-dell-laptop?lang=en" target="_blank" rel="nofollow ugc noopener noreferrer">https://www.dell.com/support/article/us/en/19/sln131497/how-to-run-the-lcd-built-in-self-test-on-a-dell-laptop?lang=en

Is your screen lo longer working after you've updated your computer through dell update?

That's what has happened to mine. I've had screen flickering after updates in the past too.

Has anybody been able to resolve this issue?

Welcome to the Dell Community  @Paddy89 

We are still waiting for  @bluelemon  to reply with their exact model number.

Until then you may want to start a new Discussion with your details and exact model number.

Best regards,

U2

oh sorry, it an 9570 xps 32gb ram

@bluelemon 

Have you updated any drivers or BIOS recently???

Where you able to run the LCD Built-in Self-Test (BIST)???

Hold down the " D " key and power-on.

Regards,

U2

oh sorry, it an 9570 xps 32gib ram

Yes I have updated recently using dell update. I can't remember exactly what the updates were named.

I have successfully run the display test with all colours displayed correctly. The laptop does not work when connected to external display either.