IBM 560 - Manual (Page 75)

Return Codes
The following return codes are stored in both the AL (AX) register
and the return code field of the output parameter.
h No Error
53h SMAPI function is not available
81h Invalid parameter
86h Function is not supported
9 h System error
91h System is invalid
92h System is busy
A h Device error (Disk Read Error)
A1h Device is busy
A2h Device is not attached
A3h Device is disabled
A4h Request parameter is out of range
A5h Request parameter is not accepted
All other values are reserved.
ThinkPad 560/560E SMAPI BIOS A-11