Can't access custom methods and any added file using AJAX in Opencart

I have a custom function that calls a product file in a controller via AJAX. The problem is when the AJAX function is called, it shows a network error: 404 http: //localhost/opencart/index.php? Route = product / product / checkzipcode was not found in the Firebug console and nothing happens at all.

The AJAX function is picking the url instead of the method I think.

I double checked the url and function in the file. Both are correct there too. I also added a new jQuery file to the header and the same error appears again that the file is missing:

Network error: 404.

I think there is a problem with my .htaccess file or php.ini file because the errors are the same with two different things.

How do I access a file on my host via AJAX?