You must modify the model file of product at catalog/model/product.php by adding m.image AS manufacturer_img,
to the existing select query of getProduct function. See snippet below:
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$query = $this->db->query("SELECT DISTINCT *, pd.name AS name, p.image, m.name AS manufacturer, `m.image AS manufacturer_img,` (SELECT price ...
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then add 'manufacturer_img' => $query->row['manufacturer_img'],
to the return array:
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'manufacturer_id' => $query->row['manufacturer_id'],
'manufacturer_img' => $query->row['manufacturer_img'],
'manufacturer' => $query->row['manufacturer'],
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Finally on the featured module catalog/controller/module/featured.php
as you've did, you can add this snippet code to get manufacturer related data of the product:
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'manufacturer' => $product_info['manufacturer'],
'manufacturer_id' => $product_info['manufacturer_id'],
'manufacturer_img'=> $product_info['manufacturer_img'],