Laravel 5-AJAX不起作用

I have one problem with my script on LARAVEL 5. This is my route:

Route::get('cms/section/addCategory', 'Cms\SectionController@showCategory');
Route::post('cms/section/addCategory', 'Cms\SectionController@addCategory');

Controller:

// SHOW FORM WITH ADD CATEGORY
    public function showCategory() 
    {
        if (Sentinel::hasAnyAccess(['section.create']))
        {
            return view('cms.viewSystem.section.addCategory');
        }
        else
        {
            return view('cms.viewSystem.error');
        }
    }

    // ADD NEW CATEGORY
    public function addCategory()
    {
        return http_response_code(200);
    }

Ajax Script:

$(document).ready(function() {
    $('form.ajax input[type=submit]').click(function(){
        $.ajax({
            type:    'POST',
            utl:         $('form.ajax').attr('action'),
            data:        new FormData($('form.ajax')[0]),
            processData: false,
            contentType: false
        }).then(
            function(error) {
                console.log('good'+error);
            },
            function() {
                console.log('bad');
            }
        );

        event.preventDefault();
    })
});

And when I add http_response_code script working good but when I change value for 500 I see in console still informations for error 200... Have you any ideas?