Help from Pre Help Error State

As per IBM's Help key documentation
http://publib.boulder.ibm.com/cgi-bin/bookmgr/BOOKS/CO2E2001/16.2.2.2?DT=19950629163252

//QUOTE
The workstation operator uses the Help key during an error condition to
request that the AS/400 system send data about the error to the display.
The 5494 sends a SIGNAL command to the AS/400 system containing columns 2
through 5 (which is the error code) of the error line in the user bytes of
the SIGNAL command on the LU-LU flow. If the workstation operator uses the
Help key a second time, bytes 2 through 5 of the error line return to the
AS/400 system.
//ENDQUOTE

It seems that either:
1. this isn't implemented,
2. it doesn't work,
3. I don't know how to get it to work.

If it's 3, how do I get it to work.
If it's 1 or 2, what's the status?

Thanks.
-Mark