Auxiliary HVAC Heater Pump - Operation

OPERATION

The auxiliary HVAC heater pump for the Hybrid Electric Vehicle (HEV) provides engine coolant flow through the front and rear heater cores during gasoline and electric motor operating modes.

The auxiliary HVAC heater pump is controlled by the A/C-heater control and has a variable flow rate of approximately 8 - 19 liters (2 - 5 gallons) per minute.

When the gasoline engine is operating below 1000 rpm, the auxiliary HVAC heater pump boosts engine coolant flow through the heater cores at the rate of 8 liters (2 gallons) per minute. When in electric operating mode, the A/C-heater control determines coolant flow rate based on infrared sensor data and customer temperature settings.

The auxiliary HVAC heater pump is connected to the Powertrain control Module (PCM) via a Local Interconnect Network (LIN) bus. The A/C-heater control sends a flow rate command message to the Front Control Module (FCM) over the Controller Area Network (CAN) B bus. The FCM then converts and broadcasts the message over the CAN C bus to the PCM. The PCM converts the gallons per minute command from the A/C-heater control to a pump target RPM. If the A/C-heater control sends a non-zero flow rate command to the PCM and the PCM responds with a zero flow rate actual message, a Diagnostic Trouble Code (DTC) will set.

The auxiliary HVAC heater pump can be actuated and diagnosed using a scan tool Testing and Inspection.

NOTE: The auxiliary HVAC heater pump is of the identical design as the electric coolant pump for the Traction Power Inverter Module (TPIM), but is NOT interchangeable with the TPIM coolant pump due to different pump software.

The auxiliary HVAC heater pump cannot be adjusted or repaired and must be replaced if inoperative or damaged.