Principle of heating circuit for old Buick Excelle oxygen sensor

Circuit Description: The ECM provides a voltage of about 0.45V between terminals M 12 and M29 (if measured with a 10 megohm digital voltmeter, the reading may be only 0.32V). The voltage of the front heated oxygen sensor A (HO2S 1) varies from 1 V (exhaust gas is too rich) to 0. 10 V (exhaust gas is too thin). When the temperature is lower than 315 C (600 F), the oxygen sensor is like an open circuit, and no voltage is generated. Open circuit or low temperature of oxygen sensor will lead to "open loop" operation.

If the front heated oxygen sensor leads, connectors or terminals are damaged, the entire front heated oxygen sensor assembly must be replaced. Never attempt to repair wires, connectors or terminals. Clean reference air must be provided for the oxygen sensor to work normally. Clean reference air is obtained through the wire of the front heated oxygen sensor. Repairing wires, connectors or terminals will cause reference air blockage, which will reduce the performance of the front heated oxygen sensor.