The function replaces the second occurrence of a specific character in a string with a different character.

[CODE]:
```python
def replace_second_occurrence(string, target_character, replacement_character):
    first_index = string.find(target_character)
    second_index = string.find(target_character, first_index + 1)
    if second_index != -1:
        return string[:second_index] + replacement_character + string[second_index + 1:]
    else:
        return string
```

This code snippet defines a function `replace_second_occurrence` that takes three arguments: the input string, the target character to be replaced, and the replacement character. It finds the first occurrence of the target character in the string, and then finds the second occurrence starting from the index of the first occurrence. If a second occurrence is found, it replaces that character with the replacement character and returns the modified string. If a second occurrence is not found, it returns the original string.