Oxygen Sensor: Description and Operation

CIRCUIT OPERATION
There are four heated oxygen sensor used on this vehicle. Power for the heated oxygen sensors is supplied on circuit A142 when the contacts in the Automatic Shut Down (ASD) relay are CLOSED. Battery voltage for the contact side is supplied on circuit A14. This circuit is HOT at all times and protected by a fusible link located near the auxiliary jumper post on the left toe box.

Power for the coil side of the ASD relay is supplied on circuit F12. This circuit is HOT when the ignition switch is in the START or RUN position. Ground for the coil side of the relay is controlled by the Powertrain Control Module (PCM) on circuit K51.

When the PCM supplies a ground path for circuit K51 the contacts in the ASD relay CLOSE connecting circuits A14 and A142. Circuit A142 powers the heated oxygen sensors and is double crimped at the ASD relay to supply an ASD relay energized input to the PCM.

Circuit K41 delivers the signal from the left upstream heated oxygen sensor to the PCM.

Circuit K241 delivers the signal from the right upstream heated oxygen sensor to the PCM.

Circuit K341 delivers the signal from the left downstream heated oxygen sensor to the PCM.

Circuit K141 delivers the signal from the right downstream heated oxygen sensor to the PCM.

The PCM provides a ground for the left and right heated oxygen sensor signals through circuit K4. Circuit K4 connects to cavity 4 of the PCM connector.

Circuit Z12 provides the ground path for the heater circuits in the sensors.