What to run fnd_web_sec.change_password as a user other than apps

We have requirenment to use fnd_web_sec.change_password as an API to change R12 front end password. So we want to run it from an account other than APPS. The procedure uses AUTH CURRENT USER and references various tables and functions etc. I have granted access to all these to the new user I wish to run fnd_web_sec.change_password. And yet still it does not work.

Logged on as new user HITACHI we get:

SQL> DECLARE stat VARCHAR2(30);
BEGIN stat := fnd_web_sec.change_password('AJARLSON','Welcome12') ;
IF stat <> 'Y' THEN RAISE_APPLICATION_ERROR(-20001,'Fail - ' || fnd_message.get);