Reverse node reference
I found a solution to this issue by performing a query on 'field_data_field_vehicle_reference' table. 

For my case, the solution can be something like this:

function engines_of_vehicle($vehicle) {
  $nid = $vehicle-&gt;nid;

  // get all engine nids referenced to this vehicle
  $engine_nids = db_query('SELECT ref.entity_id FROM {field_data_field_vehicle_reference} ref WHERE ref.field_vehicle_reference_nid  =:nid AND ref.bundle =:bundle', array(':nid' =&gt; $nid, ':bundle' =&gt; 'engine'))-&gt;fetchCol();

  //load all engines referenced to this nid
  $engines = node_load_multiple($engine_nids);

  return $engines;    
}