O2 Sensor

O2 sensor is mounted in front exhaust pipe to measure O2 content in exhaust gas. Heating element, energized through terminal 87 of fuel pump relay, is used to insure constant operating temperature of O2 sensor. When operating temperature range, which starts at 572° F (300°C), is reached, O2 sensor sends voltage signal to ECU. Rich mixture will give signal of more than .5 volt while lean mixture will give signal of less than .5 volt.