-3403D error

Same Issue, I actually have the install disc and "D" isn't doing anything. Holding "OPTION" won't take me to the boot selection anymore either.

This is the same message that I received . My Thunderbolt port doesn't work and I did test system for that reason.
MacBook Pro Mid 2010
I was trying to connect My Passport Pro 4TB

Same here. MacBook Pro mid-2010. Having problems since Yosemite install a month or two ago. Nothing happens when I try to boot holding down the d key. The system just sits until I release the d key, at which time it reboots in normal mode. Option-d causes the error everyone else is getting here.

To use the internet for the apple hardware test, your Mac had to ship with at least Lion. Otherwise you have to have the install dvd that came with the Mac. Not a retail version, but the machine specific software. https://support.apple.com/en-us/HT201257

This is straight from someone at Apple, "That -3403D code actually means there was an issue with your Mac software configuration"

To all that get that code. It means your Mac cannot do the hardware test from the internet. You need the install disk that has the hardware test on it. Then you boot it and hold down D or Command D at startup.

Very strange i am having the same today? Coincidence?! I am trying internet recovery....

my ginger's solution is what worked for me. I can't do internet recovery on my mac--it's a bit too old. I used the dvd that came with the mac and that worked fine. Showed no hardware errors, but worked. The overall problem I was having was with the video card. Got that replaced and I'm back in business.

Created bootable El Capitan USB / Installed fresh version of El Capitan / Restored data with Time Machine / Voila

I have this same issue but mine has lines on it won't let me boot up regarly any more.

I first also had trouble. Funny thing was that with the power connected the led in the connector near the laptop was not green or range but not doing anything. Then I disconnected the connector to the white square block (with power still connected) and the led was again green. Very strange! Then the laptop booted and I could do the restore process (Created bootable El Capitan USB / Installed fresh version of El Capitan / Restored data with Time Machine ).

While this may be true, it is odd that the machine appears to attempt to load the hardware test (it goes through all the correct motions before bringing us to the -3404D error). Further, why not simply give a message like, "Sorry, hardware test via the internet is not supported on this Mac," rather than some unhelpful, cryptic message?

Finally, determining if your computer supports loading Apple Hardware Diagnostics over the internet isn't necessarily easy to do using the info from Apple. Quoted from their webpage, "Some Macintosh computers that shipped with OS X Lion and later support the use of Apple Hardware Test over the Internet. These computers will start up to an Internet-based version of AHT if the hard drive does not contain AHT."

Some? How helpful is that? Why don't we throw in "may" and "possibly" and how about "we don't really know" for good measure.

I have an early 2011 MBP 13 that does do the AHT over the internet, and a Mid 2010 that doesn't, so for the 13s that appears to be the cutoff. How hard was that, Apple? FFS

2010 and older Mac's that run Snow Leopard or older. Have to use the install disk for AHT. Some 2011 or newer with a smc and efi update can run the online diagnostics. Usually the update is part of a software update. If you have the original install disks, you don't need internet diagnostics. This is because after Snow Leopard, all operating systems came by way of a download from apple, if not preinstalled. The reinstall and the utilities is on line. The early 2011 that came with Snow Leopard generally can't use the online diagnostics. As a general rule. If your computer came with Lion or newer, you use the online diagnostics.

HI, I do have the original install disks for my iMac 27-mid 2010 but even so always get the same error message mentioned on this thread (3403D) when I try to run the ADT.