A glow sensor provides functions of both a diesel engine glow plug and an ion sensor for sensing engine combustion initiation and characteristics. A ceramic flat plate glow sensor element is carried by a tubular ceramic sleeve and insulating material in a metal shell. The element includes a ceramic flat plate having a glow tip, on an inner end with a heating element on one side and an ion sensor electrode on the other printed in electrically conductive ink. Printed conductors on both sides connect the heating element and ion sensor with an outer end of the glow sensor element for connection with an electric power source. An insulating coating protects the heating element and conductors from exposure to combustion gases. Various flat plate mounting embodiments are disclosed.