Trying to mount an ext2 / ext3 / ext4 device using external drivers on OSX might bring up the following error:

disk media is not present

in:
sudo dmesg

To fix that a virtual machine helped.

Attaching the external drive using usb, creating a filter for that usb device to forward it to the ubuntu based VM.

Run
fdisk -l

to find the right device.
E.g. /dev/sdd

Now go with fsck.ext3 (for ext3 only)

fsck -y /dev/sdd

-y means answer every question with yes.

For a 2 TB HDD that might take up to several hours, but after that is finished, you can try to mount the drive again.