In contrast to the rest of the tomb, this rough earthen passage is not lined with masonry. At various points along the tunnel, sections of the walls have crumbled, as if something had dug small tunnels in the walls that subsequently collapsed.
This tunnel turns twice and ends at the secret door that Jabari wanted to smash through. Again, it is obvious on the inside-side how to open it, and that first one can only be opened from the secret side.
There is nothing of interest in the tunnel, nor any explanation for why it exists.