Очистить у всех элементов поле (например DETAIL_TEXT)

CModule::IncludeModule('iblock');
$IBLOCK_ID = 129;
$arSelect = Array("ID", "IBLOCK_ID", "NAME","DETAIL_TEXT");
$arFilter = Array("IBLOCK_ID"=>$IBLOCK_ID, "ACTIVE_DATE"=>"Y", "ACTIVE"=>"Y");
 
$res = CIBlockElement::GetList(Array(), $arFilter, false, Array("nPageSize"=>9999), $arSelect);
while($ob = $res->GetNextElement()){
    $arFields = $ob->GetFields();
    if (!empty($arFields['DETAIL_TEXT'])){
                               print_r($arFields['NAME'].' - ');
                               $el = new CIBlockElement;
                               $arLoadProductArray = Array(
                                               "DETAIL_TEXT"    => "",
                                 );
                               $PRODUCT_ID = $arFields['ID'];
                               $res1 = $el->Update($PRODUCT_ID, $arLoadProductArray);
    }
}