Hello,
the password change is automatic from IdM to all target systems if you have enabled the tasks in repository and the password (mx_encrypted_password) can trigger the Modify-workflow.
Standard connector works fine for password change from IdM to ABAP.
Will be you having UI-functionality also to reset AD-passwords in IdM?
One thing to be noted is that; you don't most likely want IdM to send the newly resetted AD-password back to AD.
If you don't have UI tasks etc that reset the AD-password in IdM then you can just disable the password change from IdM to AD.
If you need to reset the AD-password also in IdM then you probably want to have small customization in place that detects where the password was changed and skip the AD-password change but let the ABAP-password change to proceed.
regards, Tero