From Tim Clarke
   If it's an actual read error on the IML boot record and it couldn't recover (it tries 20 different 5-sector records for a Type-3) then the area at the "end" of the drive's capacity is suspect. Backup operational partitions and do an LLFormat from Advanced Diagnostics without clearing the "grown defect list". Then Restore System Partition and then verify IML is O.K. before reloading operational partitions. 

  IML errors include problems with Initial Machine Load (IML) or Initial Program Load (IPL). Most of these errors can be corrected without replacing any FRUs. IML errors are associated with: 
    An I999XXXX error is displayed. 
    Computer powers-on without POST error, but operating system does not work. 
    The system starts up in BASIC. 

IML and IPL errors can be caused by any of the following conditions: 
    Invalid selectable drive startup sequence (default drive not in startup sequence) 
    Operating system not found 
    IML code not found 
    Related hardware failure (SCSI adapter, hard disk, SCSI cable) 
    Unrelated hardware failure (misleading error due to problem on SCSI Bus). 

Checking Startup Sequence and Hard Disk Drive
1. Start computer from RefDisk, Main Menu > Set Features. 
2. Select Set Startup Sequence, is default HD (usually ID6) in startup sequence?
       If not, follow instructions on the screen, then return to Step 2. 
3. Default drive IS in startup sequence, exit from screen and Main Menu, then go to step 5.
    Default drive NOT in startup sequence, follow instructions on the screen, then continue with step 4. 
4. Remove RefDisk, power-off computer, then power-on computer.
       "F1" (Insert Diskette) icon appears, no operating system found. Go to step 5.
        "Not OK" icon appears, system cannot access System Partition. Try updating system programs.
5. Install OS on device in startup sequence -OR- change startup sequence to include device with an OS
      Power-on computer, check for normal power-up sequence and run advanced diagnostic tests.
      If problem still exists, suspect SCSI controller, then hard disk drive.

NOTES:
Password Jumper: 
   It may be necessary to move the power-on password jumper (J22-Bermuda, JMP1=Lacuna/85, J10-90, J16-95) to enable an IML to the reference diskette in drive A. Moving this jumper forces stage 1 POST routine to branch to the diskette, rather than attempt to load stage 2 from the Fixed disk system partition. (A reference diskette must be present in the a: drive)

     The Stage 2 POST code on reference diskette is identical to the code loaded onto system partition. Moving this jumper sets all default values, except ASCII terminal mode. Moving the Power-On password jumper is effective for only 1 Power-On cycle because stage 1 POST tracks (records) the position of the jumper each time it is run.

ASCII Terminal Mode: 
   If ASCII terminal mode is set (96-8N1, Visible in information panel), the battery voltage must be removed from the planar to reset it. (Slide stiff paper under the battery clip for approx 10 to 15 minutes).

   ASCII terminal mode will be automatically set by stage 1 POST if there is no primary video adapter detected (XGA adapter is missing from the system).

NOTE: Complex based "Complex", CPU on planar "planar", both "System"

I999xxxx Error Codes

I999 00X5	Reference Diskette recovery prevented  - Power Off computer  - Toggle Password Override Jumper - Power On computer
Restore the System Partition for these errors
I999 001X  I999 002X  I999 003X  I999 004X  I999 006X  I999 007X  I999 009X    X can be any number	No valid disk IML record found on HD  Disk IML record load (read) error  Disk IML record incompatible w/planar  Disk IML record incompatible w/Complex Disk Stage 2 image load read error  Disk Stage 2 checksum (read) error  System BIOS newer than Disk IML Partition  Only valid when running system from hard disk:  - Restore System Partition
Boot with a valid reference diskette for these errors
I999 00X1  I999 00X2  I999 00X3  I999 00X4  I999 00X5 I999 00X6  I999 00X7  I999 00X9 Power On Password jumper (POP) J22-Bermuda, JMP1=Lacuna/85, J10-90, J16-95	Invalid diskette IML record  Diskette IML record load (read) error  Diskette IML record incompatible w/planar Diskette IML record incompatible w/complex  Diskette IML Recovery prevented    Power-Down, Toggle POP, Power-Up Diskette Stage 2 IML read error  Diskette Stage 2 IML checksum error  System BIOS newer than Diskette BIOS  Only valid when running system from Ref Disk:  - Restart computer from Refdisk - If same error appears, try new Refdisk
I999 0053, I999 0054  I999 0056, I999 0057  I999 0059, I999 0063  I999 0067, I999 0069	Only valid when running system from Ref Disk:  - Restart computer from Refdisk  - If same error appears, try new Refdisk
I999 0301	No bootable device found, HD or floppy  This may be a hardware failure Check:  - Cabling  - Termination - Adapter / Controller  - Hard drive
I999 0302	Invalid disk boot record (missing OS)  - Install an operating system  - check for a valid startup sequence  - are all devices in startup-sequence present?
I999 0303	System Partition boot failure  - Restore System Partition
I999 0304	No bootable device found with ASCII-console  Probably no operation system installed  - Install operation system  - Does startup sequence contain default drive?
I999 0305	No startable device found  Probably no operation system installed  - Install operation system  - Does startup sequence contain default drive?
I999 0306	Invalid startup.  - Trying to start from CD-ROM drive  - Restart computer from startable Floppy or HD.
I999 0401  (Fatal)	Unauthorized Access  Clear POP before replacing parts!  - Replace Planar or Complex  (Whichever contains the ROM)
I999 0402   (Fatal) I999 0403   (Fatal)	- Replace Planar or complex  (Whichever contains the ROM)
I999 0600   (Fatal) I999 0607   (Fatal) I999 0609   (Fatal)	IBM Overlay errors  Restore System Partition
I999 80XX	ThinkPad system partition  1. Reseat HD. Check Startup Sequence  2. Hard Disk Drive  3. System Board

Usually Fatal I999xxx Errors
The following errors normally require processor FRU replacement:-
I9990401 - Unauthorized access.
I9990402 - Missing ROM IBM Copyright notice
I9990403 - Non IBM IML routine
I9990600 - IML Overlay Logistics Error
I9990607 - IML Overlay Checksum Error
I9990609 - IML Overlay ID Error