Found the answer to my question.its indeed true about non covered causing covered part to fail
Failure of a covered part under normal service. A covered part has failed when it can no longer perform the function for which it was designed solely due to its condition, and not due to the action or inaction of any non-covered parts. In addition, a Failure will be deemed to have occurred when a covered part has worn beyond the manufacturer's tolerances allowed for the particular Vehicle at the odometer reading when the problem occurs.