IBM X23 - Manual (Page 6)

Hard disk drive replacement strategy
Always try to run a low-level format before replacing a hard
disk drive.
Attention
The drive startup sequence in the computer you are
servicing might have been changed. Be extremely
careful during write operations such as copying,
saving, or formatting. If you select an incorrect drive,
data or programs can be overwritten.
How to use error messages
Use the error codes displayed on the screen to diagnose
failures. If more than one error code is displayed, begin the
diagnosis with the first error code. Whatever causes the
first error code may also cause false error codes. If no
error code is displayed, see if the error symptom is listed
in the Symptom-to-FRU Index for the computer you are
servicing.
How to read POST error messages
POST error messages are displayed on the screen as
three, four, five, or eight digits. The error messages that
can be displayed as shorter POST messages are
highlighted in this index. Some digits have one meaning for
SCSI errors and a different meaning for non-SCSI errors.
The following example shows which digits display the
shorter POST error messages and also defines the SCSI
information in each digit of an eight-digit error message.
Shorter POST Messages
Reserved
Device Code
0 0 0 0 0 0 0 0
ID (SCSI)
Logical Unit Number (SCSI)
Slot Number (SCSI)
Size (SCSI)
Each SCSI device is assigned a unique SCSI ID. Duplicate
SCSI ID settings can generate a false error message. Use
the SCSI ID to determine whether an error message is
coming from an internal or an external device.
2 ThinkPad X20, X21, X22, X23, X24