Oxygen Sensor Circuit Operation

Circuit A14 is a bus bar in the PDC, and connects to battery voltage. The contact side of the Automatic Shut-Down (ASD) relay connects circuit A14 and circuit A142. A 20 Amp fuse in the PDC protects circuits A14 and A142

Circuit A14 also supplies voltage to the coil side of the ASD relay. The Powertrain Control Module (PCM) controls the ground path circuit for the coil side of the ASD relay on circuit K51. Circuit K51 connects to cavity 18 of the PCM connector

Circuit A142 splices to supply voltage for the upstream and downstream heated oxygen sensors. Circuit A142 connects to cavity 4 of each heated oxygen sensor connector.

The A142 circuit also splices to cavity 42 of the PCM. The input provided by circuit A142 at cavity 42 tells the PCM that the ASD relay is energized.

Circuit K41 delivers the signal from the upstream heated oxygen sensor to the PCM. Circuit K41 connects to cavity 8 of the PCM and cavity 2 of the sensor connector.

Circuit K141 delivers the signal from the downstream heated oxygen sensor to the PCM. Circuit K141 connects to cavity 7 of the PCM and cavity 2 of the sensor connector.

The PCM provides a ground for the upstream and downstream heated oxygen sensor signals (circuit K41 and K141) through circuit K4. Circuit K4 connects to cavity 51 of the PCM connector and cavity 1 the upstream and downstream heated oxygen sensor connectors.

Circuit Z1 provides a ground for the heater circuits in each sensor. The Z1 circuit connects to cavity 3 of each sensor. Circuit Z1 terminates at the left side radiator closure panel.