The development of new systems to reduce exhaust gases is being investigated in response to OBD-II regulations and regulations all over the world relating to the introduction of low exhaust gas vehicles (LEV, ULEV, STEP3, STEP4). We have developed a highly responsive thermistor type catalyst temperature sensor that is very accurate, highly heat resistant, has a wide detection range, and that can be used in exhaust gas cleansing systems.The key technologies used in this new catalyst temperature sensor are: 1Wide detection range: The thermistor is of a network construction that comprises a semi-conductor with a new Y-Cr-Mn perovskite crystal structure and an insulator. The temperature range can be set by changing the proportions of semi-conductor and insulator. There are three settings (accuracy of within ±10°C) 100°C to 600°C- For De-NOx catalyst control 200°C to 700°C- For NOx catalyst control in direct gasoline injection engines 600°C to 1,000°C- For high speed fuel consumption reduction systems and misfiring detection systems 2High responsiveness (thermal time constant τ = 8 seconds): Use of microchip for thermistor element and optimal design of heat sensor 3High accuracy (within ±10°C): Atomization of thermistor materials and uniform mixing 4High reliability: Use of highly heat resistant and vibration resistant design means that accuracy change after a reliability test are within ±5°C. This sensor will be used on vehicles to be released in 1999 in Japan and 2000 in Europe.