Symptom
Detailed information on removing CMOS Batteries FRU 02K6686.

Possible A Series Post Errors that indicate CMOS (RTC) battery should be replaced:

• 0250 systems battery error
• 0251 System CMOS checksum bad
• 0260 System Timer error
• 0270 Real-Time Clock Error

NOTE: Mini PCI Card must be removed first before, CMOS Battery is accessible.

Affected configurations
All IBM ThinkPad A20m, A21m, A22m, A20p, A21e (2628), A21p, A22p systems.

Solution
Remove and replace the CMOS battery.

1. Loosen the screw 1, but do not remove it.
2. Lift memory door off.

For A20m/p, A21m/p series

NOTE: The illustration shows the combo card. Connector (A) is for the LAN feature and (B) is for the modem feature. This slot also supports a Mini PCI modem card or Mini PCI network card. Step 5 depends on the card type. Disconnect either (A), (B) or both. When installing the card, do the following:

• With the notched end of the card toward the socket, insert the card into the socket, then press it firmly. Pivot the card until it snaps into place. Make sure that the card is firmly fixed in the slot and does not move easily.
• Make sure that the connector (A) is placed under the card when reinstalling the Mini PCI adapter.

For A22m/p series

NOTE: The illustration shows the combo card. Connector (A) is for the LAN feature and (B) is for the modem feature. This slot also supports a Mini PCI modem card or Mini PCI network card. Step 4 depends on the card type. Disconnect either (A), (B) or both. When installing: With the notched end of the card toward the socket, insert the card into the socket, then press it firmly. Pivot the card until it snaps into place. Make sure that the card is firmly fixed in the slot and does not move easily.

CAUTION: There is a danger of an explosion if the backup battery is incorrectly replaced. The lithium battery (IBM P/N 02K6572 UL-recognized component [file no. MH12210]) contains lithium and can explode if it is not properly handled or disposed of. Replace only with a battery of the same type. To avoid possible injury or death, do not: (1) throw or immerse the battery into water, (2) allow it to heat to more than 100°C (212°F), or (3) attempt to repair or disassemble it. Dispose of it as required by local ordinances or regulations.