The keypad connection of Nokia X3-02 is assembled on a Flexible cable wire ( Flex Connection )
You may need to first visually check the flex cable if showed some damaged. The solution below shows the spots on Nokia X3-02 keypad flex connection where to check most importantly. If the keypad flex is already damaged, you may need to replace it with a new replacement spare.
Each keys were group in one connection, if only one or two keys are not working, you may refer to the solution below to determine which and where to reconnect the non responding particular keys.
Nokia X3-02 keypad flex cable connection
If the solution above does not help and solved the problem or if the keypad flex is working perfectly okay, You may then proceed to check and or replace the Nokia X3-02 Keypad filter IC, which is located or mounted on the main PCB board near to the keypad pin connector.
Nokia X3-02 keypad filter IC mounting location
There are other two EMI-ESD filter mounted just below it, and these other two holds the LCD display signal filtering. Just do some precautions in handling the keypad filter IC and avoid hitting the other two chips for it will result to display problem. Replacing the keypad filter IC is the next option if the keypad flex is okay or already tried installing a new replacement keypad flex on it and it is the only possible way to fix and repair nokia x3-02 with a not working keypad problem.