Bosch Planar Oxygen Sensors deliver best-in-class performance.Driven by the need to meet U.S. EPA requirements for lower exhaust emissions, Bosch developed the revolutionary planar sensor. The planar sensor "lights off," or reaches operating temperature, in approximately 10 to 12 seconds. That's over two times faster than a conventional thimble type oxygen sensor. This quicker light-off time reduces emissions by over 50% during the cold start phase, when harmful emissions are highest.