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Cooled EGR is one of the engine technologies that has been certified by the EPA for on-highway heavy duty diesel engines to meet the EPA October 2002 2.5 g/bhp-hr NMHC + NOx and 0.1 g/bhp-hr particulate matter exhaust emission regulation. Cooled EGR as the primary exhaust emission control reduction technology also minimizes the fuel economy penalty associated with this exhaust emission regulation. The cooled EGR system however requires precise EGR rate of flow control in a very unfriendly environment that includes acidic exhaust gas condensates, static pressures up to 4 Bar, temperatures over the entire range of -40 to 250° C, and high engine vibration levels. Several technologies have been proposed and evaluated to achieve a closed loop feedback signal for the EGR flow control valve and VGT (Variable Geometry Turbocharger) vane position.

Ultra Low Emission Vehicle (ULEV) and proposed Super Low Emission Vehicle (SULEV) requirements along with Lean Burn Systems will require improved Engine Management Systems and new catalyst technologies. High performance, reliable exhaust gas/catalyst temperature sensors are one of the key enabling technologies needed for these next generation engine management systems and catalysts. The demand for accurate, high temperature Exhaust Gas Temperature Sensors (EGTS) is growing quickly. Gasoline direct injection engine lean NOx catalyst traps, On Board Diagnostic catalyst monitoring systems, Diesel engine active lean NOx catalyst systems and large Diesel engine diagnostics and protection functions all require accurate measurement of exhaust gas temperature over a wide range. Added to these requirements are the need for short response times, low production costs, and a high sensitivity linear signal for direct input into engine management controllers.