Your CICS map tries to display a character which is not available in the character set of mainframe.
It is better to check all the values the map tries to display in the variable field. You can check them by writing some TSQ or using DISPLAY statement for each variable field of the map.
Mostly the error will come from some special or non-displayable characters.With this in mind, You need to identify potential list of fields.
Try to alter the special characters of each field (one by one) by some SUBSTRing manipulation commands & re-execute the transaction after each variable modification.
This way you can exactly locate which variable and character causing this error.
After wards identify the source of this value. If it comes from any DB2 Table or File then you need to change all the occurrences in the Table / File.
If you can not correct the source then live with some work around and also correct other programs which might try to display these values.