Oxygen sensors, also known as Lambda sensors or O2 sensors among some vehicle manufacturers, are among the most sensitive and critical components on your car's engine. Earlier fuel injection systems employed one oxygen sensor in the exhaust system to maintain closed-loop air/fuel mixture control. However, today's engines may use as many as four sensors, which monitor not only exhaust gas oxygen content but catalytic converter efficiency as well. In order to perform these functions properly, the sensors must adhere to OE standards within incredibly close tolerances. A malfunctioning or incorrectly calibrated oxygen sensor can hurt drivability and illuminate the malfunction indicator, resulting in costly and time-consuming repairs. DENSO First Time Fit oxygen sensors are designed to meet those tolerances and more. The DENSO oxygen sensor catalog offers one of the most complete product lines in the industry, from Acura to Volvo.