DTC P1ECA or P1EC9
Diagnostic Instructions
DTC Descriptors
DTC P1ECA: A/C Compressor Motor Instantaneous High Voltage
DTC P1EC9: A/C Compressor Motor Instantaneous High Current
Circuit/System Description
The AC compressor function is to provide refrigerant flow in the AC refrigerant loop to help cool down the cabin, help dehumidify the air in a defrost mode and help maintain the battery temperature. Rather than a more typical pulley, the A/C compressor uses a 3-phase alternating current, high voltage electric motor to operate. It has an on-board inverter that takes High Voltage direct current from the vehicle's High Voltage Battery and inverts it to alternating current for the motor. The AC compressor shall be activated when any of the three following events occur:
• | The customer pushes the AC button |
• | The HVAC control, in AUTO mode, requests the electric AC compressor on to help in cooling the cabin or removing moisture in the defrost mode |
• | The High Voltage Battery Thermal System requests the AC compressor on to help maintain the battery temperature |
The Hybrid/EV Powertrain Control Module 2 uses values from the A/C refrigerant pressure transducers, A/C refrigerant thermistor, duct temperature sensors, ambient air temperature sensor, passenger compartment temperature sensor, evaporator temperature sensor, battery cell temperature sensors, battery coolant temperature sensors and battery coolant pumps to determine the speed at which the compressor will operate. This speed request message is sent from the Hybrid/EV Powertrain Control Module 2 to the A/C compressor control module via GM LAN message.
Conditions for Running the DTC
DTC P1ECA
• | System voltage is above 10.25 V. |
• | Vehicle is in Run Mode or Charging Mode |
DTC P1EC9
• | System voltage is above 10.25 V. |
• | Vehicle is in Run Mode or Charging Mode |
• | Compressor Speed Request is greater than 0 RPM |
Conditions for Setting the DTC
DTC P1ECA
Sets when the high voltage to the module is greater than 480 V for 3 seconds
DTC P1EC9
Sets when DC Link is above threshold of 60 A for 3 seconds
Action Taken When the DTC Sets
The A/C compressor control module is disabled but will retry once the compressor speed request goes to 0 RPM and a new speed request greater than 0 RPM is sent.
Conditions for Clearing the DTC
The DTC can be cleared with the scan tool.
Reference Information
Schematic Reference
HVAC Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Automatic HVAC Description and Operation
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
- Verify that DTC P1ECA or P1EC9 is not set.
⇒ | If the DTC is set, verify that the A/C compressor control module and the Hybrid/EV powertrain control module 2 have the latest software and reprogramme the modules if needed. |
- Operate the vehicle within the conditions for running the DTC.
⇒ | If the DTC is set, replace the G1 A/C compressor. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
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