Making sense of error codes

[Mike Neimoyer]

Good morning, all.

First post to the group, and I'm a bit of a newbie in general, so please 
be gentle. :)  I'll provide as much information as I know how to, and if 
there's more you need, please let me know and I'll do my best!  Thanks.

Recently, I've had a tape library's autoloader stop being recognized. 
It was working just fine, and then the backup software (amanda) began 
reporting errors that it couldn't communicate.  No changes were made to 
the system and it had run a backup earlier that morning successfully. 
Multiple attempts to re-establish communications failed, checked all 
cables, verified that the system saw the device by "camcontrol devlist" 
(it did, but the unit was listed simply as "pass3" instead of the usual 
"ch0,pass3").  Was eventually told to shutdown and powercycle both 
units, but without success.

Basics:
FreeBSD 6.1-RELEASE
Dell Powervault 124t via SCSI

Checking the /var/log/messages file, after the  I see:
May 2 16:44:24 jazz kernel: sa0 at ahc1 bus 0 target 12 lun 0
May 2 16:44:24 jazz kernel: sa0: <CERTANCE ULTRIUM 2 1914> Removable
Sequential Access SCSI-3 device
May 2 16:44:24 jazz kernel: sa0: 160.000MB/s transfers (80.000MHz,
offset 127, 16bit)
May 2 16:44:24 jazz kernel: (ch0:ahc1:0:12:1): MODE SENSE(06). CDB: 1a
20 1d 0 20 0
May 2 16:44:24 jazz kernel: (ch0:ahc1:0:12:1): HARDWARE FAILURE asc:40,84
May 2 16:44:24 jazz kernel: (ch0:ahc1:0:12:1): (null)
May 2 16:44:24 jazz kernel: (ch0:ahc1:0:12:1): fatal error, failed to
attach to device
May 2 16:44:24 jazz kernel: (ch0:ahc1:0:12:1): lost device
May 2 16:44:24 jazz kernel: (ch0:ahc1:0:12:1): removing device entry

So, there is a hardware failure somewhere, but I am not sure how to 
determine if it's the internal card or the external tape library unit 
itself (in a perfect world, I'd have another tape library unit I could 
just swap out, but alas.... :)  ).

I've tried looking up the ASC (40, 84), but can't seem to find a 
agreed-upon meaning for them.  I could, quite probably in fact, simply 
not be looking in the right place.

Can any kind soul point me in the right direction for figuring this 
issue out?  Thanks!

Best,
~~Mike