Oxygen Sensor Relay: Description and Operation
O2 HEATER RELAY5.9L/8.0L Only
The oxygen (O2) sensor heater relay is located in the Powertrain Distribution Center (PDC). Relay Boxapplications and ID.
Oxygen Sensor Heater Relay:
If the vehicle is equipped with 4 oxygen sensors, a separate oxygen sensor relay is used to supply voltage to the sensor heating elements. This particular relay is used only for the 1/2 and 2/2 downstream sensors. Voltage for the other 2 sensor heating elements is supplied directly from the ASD relay. Refer to Wiring Diagrams to determine which relay is used. Electrical Diagrams
To avoid the large simultaneous current surge needed to operate all 4 sensors, power is delayed to the 2 downstream heater elements by the PCM for approximately 2 seconds.