External DB - error from __construct

Hi!

I need to connect my app to external database, but when I chage parameters I getting error from __construct function:

Code:

Unable to connect to database server using the specified settings.
Filename: core/MY_Controller.php

Line Number: 8

This is fragment of this file:

PHP Code:

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');

class MY_Controller extends CI_Controller {

 protected $UserData;

 public function __construct() {
 parent::__construct();        // line 8

 $UserData = $this->ion_auth->user()->row();

 } 


When I delete the entire function, I get the same error but with another file.
Why? Maybe I forgot something?