a gas sensor includes a gas sensing element positioned at least partially within a body and exposed at a first end to measure a gas in contact with the first end . the gas sensing element defines an axial direction . a flange extends from the body in a direction transverse to the axial direction . the flange has a first side facing toward the first end and a second side facing toward a remote end of the gas sensor . an o - ring is configured to sealingly position the gas sensor within a bore . an insertion portion of the gas sensor is defined by a wall and configured to hold the o - ring . the wall of the insertion portion is spaced a distance from the body at an axial position of the o - ring to provide a gap therebetween .