Panasonic KX-TD500 System Reference Manual page 1268

4.00 Other Error Messages
Error Message
PASSWORD ERROR Assigned password is not correct.
MODE ERROR Selected mode is not correct.
COMMAND ERROR Entered command is not correct.
TYPE ERROR Selected type is not correct.
INDEX ERROR Entered index number is not correct.
ITEM ERROR Entered item number is not correct.
LOGICAL ERROR Programming data assigned in off-line mode
has some logical error.
DATA ERROR Assigned data is invalid.
Probable Cause
11-D-8
Countermeasure
Enter the correct password.
Change the mode.
Enter the correct command.
Select the correct type. (SH, AT, BT)
Enter the correct index number.
Enter the correct item number.
Assign the correct data.
Refer to the DATA ERROR No. list.