P1EC9

DTC P1ECA or P1EC9

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor
DTC P1ECA
- HV Voltage Instant Overvoltage Performance Fault

DTC P1EC9
- DC Link Instant Overcurrent

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 VICM 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 VICM to the A/C compressor control module via GM LAN message.

Conditions for Running the DTC

DTC P1ECA
* System voltage is above 9 V.
* Vehicle is in Run Mode or Charging Mode with RESS Thermal Active

DTC 1EC9
* System voltage is above 9 V.
* Vehicle is in Run Mode or Charging Mode with RESS Thermal Active
* 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 volts for 3 seconds

DTC P1EC9

Sets when DC Link is above threshhold of 60 amps for 3 seconds

Action Taken When the DTC Sets

The ACCM 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 HVAC - Automatic
Connector End View Reference

Component Connector End Views Connector End Views By Name
Description and Operation

Automatic HVAC Description and Operation HVAC - Automatic
Electrical Information Reference

* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference

Control Module References Control Module References for scan tool information

Circuit/System Verification

Verify that DTC DTC P1ECA or P1EC9 is not set.

If the DTC is set, verify that the A/C compressor control module and the VICM (HPCM2) have the latest software and reprogram the modules if needed.

Circuit/System Testing

Operate the vehicle within the conditions for running the DTC.

If the DTC is set, replace the A/C compressor control module.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.

Air Conditioning and Drive Motor Battery Cooling Compressor Replacement Air Conditioning and Drive Motor Battery Cooling Compressor Replacement