Thinkpad600 - the 0(OFF) I(ON) error when CDROM is connected

Question

My friend gave me a Thinkpad 600. Type: 2645350 S/N:55132RW
Configuration:
CPU Pentium II 233 MHz
RAM 288 MB (Internal 32 MB + 128 MB + 128 MB in expansion slots)
HDD bay: 5 GB IBM HDD
Ultraslim bay: original FDD FRU P/N 05K8874
When I switch on the Thinkpad with the new CMOS battery (which I replaced recently), I get error codes 163 and 173.
The window with error codes 163 and 173 pops up, I press OK, window with time and date settings pops up.
I set the time and date, I have to change the time and date from default values (2000-01-01; 00:00:00) to actual
values and I confirm it by pressing OK button.
I hear double beep and restart is performed. After restart no error code appears and MS-DOS from HDD 1 is loaded.
I switch off the Thinkpad.
Now when I switch on the Thinkpad second time, again the error codes 163 and 173 appears even though I set the time and date before, window with error codes 163 and 173 pops up, I press OK, window with time and date settings pops up.
I just confirm the time and date because the actual time and date remain and I confirm it by pressing OK button.
I hear double beep and restart is performed. After restart no error code appears and MS-DOS from HDD 1 is loaded.
I switch off the Thinkpad. 
When I go to Easy setup and then Test window  and I perform test with all components (System board, Memory, Display,
HDD1, FDD1, Parallel, Serial, DSP, Infrared, etc) I get test result OK for each component.
When I press CTRL + A the window with connected FRU parts appears showing that all parts are connected instead Docking Unit.
The booting order is set as: 1st FDD1, 2nd CDROM, 3rd HDD1
The problem occurs when I swap the drive in Ultraslim bay.
Now the configuration in Ultraslim bay is changed as shows below:
Configuration:
CPU Pentium II 233 MHz
RAM 288 MB (Internal 32 MB + 128 MB + 128 MB in expansion slots)
HDD bay: 5 GB IBM HDD
Ultraslim bay: original Toshiba CD ROM drive FRU P/N 05K8873
Now when I switch on the Thinkpad, again the error codes 163 and 173 appears even though I set the time
and date before, window with error codes 163 and 173 pops up, I press OK, window with time and date settings pops up.
I just confirm  the time and date because the  actual time and date remain and I confirm it by pressing OK button.
I hear double beep and restart is performed. After a less then a minute I get one beep and on the screen I see
O > I these are all flickering. I’ve found in the online manual the following
--- the 0 > I error in the manual means ----
‘This message appears when you restart your computer after you have changed
the IDE channel from 2 to 3. Power off the computer and wait at least 5
seconds; then power it on again.’
When I switch off the Thinkpad and wait more than 5 seconds and then switch on  this message appears again and
this does not solve the problem.
Does anybody know how to solve this problem with --- the 0 (OFF) > I(ON) error ---  which are displayed every time when I switch on my Thinkpad?
It seems there is some conflict in IDE bus, because when only HDD1 is connected to IDE then the Thinkpad is booting to MS-DOS and when HDD1 as well as CDROM is connected to IDE bus the Thinkpad stops always on this error message.
When I go to easy setup and then to Test window in this configuration scenario, I see the HDD1 as well as CDROM icon as Grey (Not connected??) but when I press CTRL + A, in the FRU parts window I see that only HDD and Docking unit is not connected and CD-ROM is connected.
thanks in advance
Milan

Answer 1

About the backup battery, I do not have available original backup battery FRU 02K6502 at the moment.
So I used standard 3V lithium battery type 2025 from Duracell.
Red wire is soldered to " + " side of coin battery
Black wire is soldered to " - " side of coin battery
The battery is wrapped by insulated tape.  I measured the voltage and it shows me 3 V, so I assume the battery is OK.
Even though I got error code 163 which means "time and date were not set",  they are set. And code 173 which means "Configuration data was lost", but in this case it was not lost, but has been retained.
If I disconnect the backup battery, then the time and date is lost and there is default setting. When the backup battery is connected, the time and date remains set... so based on these outcome I assume the battery is OK.