Oxygen sensor heater relays-pcm output. Radiator cooling fan relay-pcm output

Oxygen sensor heater relays-pcm output

DESCRIPTION

The 2 oxygen (O2) sensor heater relays (upstream and downstream) are located in the Powertrain Distribution Center (PDC).

OPERATION

Engines equipped with the California (NAE) Emissions Package use four O2 sensors.

Two of the four sensor heater elements (upstream sensors 1/1 and 2/1) are controlled by the upstream heater relay through output signals from the Powertrain Control Module (PCM).

The other two heater elements (downstream sensors 1/2 and 2/2) are controlled by the downstream heater relay through output signals from the PCM.

To avoid a large simultaneous current surge, power is delayed to the 2 downstream heater elements by the PCM for approximately 2 seconds.

Radiator cooling fan relay-pcm output

DESCRIPTION

The radiator cooling fan relay is a 5-pin, solenoid type, mini-relay. It is located in the Power Distribution Center (PDC). Refer to label on PDC cover for relay location.

OPERATION

The electric radiator cooling fan is controlled by the Powertrain Control Module (PCM) through the radiator cooling fan relay. The PCM will activate the relay after receiving inputs from the engine coolant temperature sensor and/or an air conditioning on/off signal. Not Equipped With A/C: The relay is energized when coolant temperature is above approximately 103C (217F). It will then de-energize when coolant temperature drops to approximately 98C (208F). Refer to Cooling Systems for additional information. Equipped With A/C: In addition to using coolant temperatures to control cooling fan operation, the cooling fan will also be engaged when the air conditioning system has been activated. Refer to Heating and Air Conditioning for additional information.