Theory Of Operation

WARNING: This page is about a different variant/trim than selected.

The Electric AC Compressor (EAC) is a self contained high voltage, 3 phase Alternating Current (AC) electric motor driven compressor with a built in microprocessor that performs operational controls and self diagnostics. Both high voltage power, to supply the compressor drive motor and low voltage power, for the internal electronic control unit (ECU) operation are required for the EAC to operate. EAC activation is performed by the Hybrid Control Processor (HCP) in Plug-in Hybrid Electric Vehicles (PHEV). The primary function of the compressor assembly is to provide cooling for both the passenger compartment and the High Voltage Battery System (HVBS). It is important to note that the vehicle can be in an inoperable state if the EAC is not operational and battery cooling is required.
At IGN-RUN/START or any hard wired wake up the HCP will wake up, activate CAN-C, CAN-3C, and CAN EPT Busses. When EAC receives the Hard Wired Wake Up signal from the (HCP) which is a sub component of the Power Inverter Module (PIM), it will power up and boot the internal EAC ECU. Once internal EAC ECU diagnostics have run and passed the EAC ECU is ready to accept serial communication commands which are used to control EAC operation and self report operational and diagnostic status to the HCP. Following the HCP power up sequence and EAC ECU initialization, High Voltage (HV), Low Voltage, Temperature, Communication, Internal Memory, Current Flow and Compressor Speed are monitored by the EAC ECU. The High Voltage supply is provided by a fused 300 Volt circuit from the PIM. The low voltage supply for EAC internal ECU operation is provided by fused B+ from the Power Distribution Center (PDC).

NOTE: This DTC is not diagnosed in the usual manner, read the entire procedure carefully! All possible EAC failure modes for the Electric Air-conditioning Compressor (EAC) have been ported to this single DTC. The actual fail condition that caused this DTC to set will be determined by the data shown in the Environmental Data associated with this particular failure. Therefore it will be necessary to record and use the associated Environmental Data from the scan tool to determine the correct diagnostic path.