Can’t Start MacBook in Diagnostic Mode
2011 MacBook OS 10.13.6.
Trying to boot Mac in diagnostic mode and getting held up on screen and message “apple.com/support” with a code below “-3403D”. Any ideas what this means?
MacBook Pro 13″
Welcome!
What was the computer doing (or not doing) that led you to run diagnostics? Knowing that may help us better help you.
Macs that old do not use Apple Diagnostics but rather Apple Hardware Test AHT). They start up differently. Do you still have have the grey install/restore disks that came with the computer? (2011 was the last year these were issued). If so, insert the disk marked as having Apple Hardware Test (AHT) and follow these instructions:
How to use Apple Hardware Test on your Mac - Apple Support
You 2011 Macbook Pro needs to be a Late 2011 to use AHT over the internet, mentioned in the "Learn More..." section of the article I linked.