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P1EC2




DTC P1EC1 or P1EC2

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 Descriptors

DTC P1EC1
- Battery Energy Control Module High Voltage Energy Communication Bus Enable Circuit Low Voltage

For symptom byte information, refer to Symptom Byte List Symptom Byte List.

Diagnostic Fault Information






Circuit/System Description

The Hybrid Powertrain Control Module 2 activates the high voltage energy management communication enable circuit when the vehicle is on. The high voltage energy management communication enable circuit wakes up the Battery Energy Control Module for serial data communication.

The Battery Energy Control Module compares the high voltage energy management communication enable hardwire signal with a Hybrid Powertrain Control Module 2 serial data message indicating that the high voltage energy management communication enable signal is active. If the high voltage energy management communication enable hardwire signal is low when the serial data message indicates it should be high, then DTC P1EC1 is set.

Conditions for Running the DTC

* The device is awake and communicating.

* The system voltage is at least 9 V.

* DTCs U2602, U180B, P1A0C, or P1A07 is not set.

Conditions for Setting the DTC

P1EC1

The ignition voltage on the high voltage energy management communication enable circuit is less than 5 V.

Action Taken When the DTC Sets

DTCs P1EC1 and P1EC2 are type A DTCs.

Conditions for Clearing the DTC

P1EC1

The ignition voltage on the high voltage energy management communication enable circuit is at least 5 V for 10 seconds.

DTCs P1EC1 and P1EC2 are type A DTCs.

Diagnostic Aids

Short to ground will also set multiple no communication codes for devices on high voltage management serial data bus.

Reference Information

Schematic Reference

* Data Communication Schematics [1][2]Electrical Diagrams

* Control Module References Programming and Relearning

Connector End View Reference

Component Connector End Views Hybrid/EV Battery Pack X1

Description and Operation

Data Link Communications Description and Operation Description and Operation

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

Scan Tool Reference

Control Module References Programming and Relearning for scan tool information

Special Tools

* EL-48900 - HEV Safety Kit

* EL-50211 - Low Voltage Jumper Harness Extension

For equivalent regional tools, refer to Special Tools Tools and Equipment.

Circuit/System Verification

1. Vehicle in Service Mode.

2. Verify that DTC P1EB9 or U185B is not set.

• If any of the DTCs are set
Refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.

• If none of the DTCs are set

3. Refer to Circuit/System Testing.

Circuit/System Testing

Danger: Always perform the High Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed.


The High Voltage Disabling procedure includes the following steps:


* Identify how to disable high voltage.


* Identify how to test for the presence of high voltage.


* Identify condition under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed.


Before working on any high voltage system, be sure to wear the following Personal Protection Equipment:


* Safety glasses with appropriate side shields when within 15 meters (50 feet) of the vehicle, either indoors or outdoors.


* Certified and up-to-date Class "0" Insulation gloves rated at 1000V with leather protectors.


- Visually and functionally inspect the gloves before use.


- Wear the Insulation gloves with leather protectors at all times when working with the high voltage battery assembly, whether the system is energized or not.


Failure to follow the procedures may result in serious injury or death.


Danger: The Volt Battery Pack will utilize an exchange program. Please consult the most recent revision of bulletin/PI #PIP4841, available in Service Information (SI), for a list of approved Volt Battery Pack service procedures. Components that may be removed and serviced without exchanging the complete battery pack are identified in the bulletin/PI. Please contact the GM Technical Assistance Center if you have any questions.


Note: Use the schematics and connector end views to identify the devices' high voltage energy management communication enable circuit terminals.

1. Vehicle OFF, disconnect the X1 harness connector at the A4 Hybrid/EV Battery Pack.

2. Vehicle in Service Mode.

3. Verify that a test lamp illuminates between the high voltage energy management communication enable circuit terminal 5 X1 and ground.

• If the test lamp does not illuminate

1. Vehicle OFF, disconnect the X1 harness connector at the T18 Battery Charger, Vehicle in Service Mode.

2. Verify a test lamp illuminates between the high voltage energy management communication enable circuit terminal 5 X1 at the A4 Hybrid/EV Battery Pack and ground.

• If the test lamp illuminates, replace the T18 Battery Charger.

• If the test lamp does not illuminate

3. Vehicle OFF, disconnect the X2 harness connector at the K114B Hybrid Powertrain Control Module 2.

4. Test for infinite resistance between the high voltage energy management communication enable circuit terminal 5 X1 at the A4 Hybrid/EV Battery Pack and ground.

• If less than infinite resistance, repair the short ground on the circuit.

• If infinite resistance

5. Test for less than 2 ohms in the high voltage energy management communication enable circuit end to end between the A4 Hybrid/EV Battery Pack terminal 5 X1 and the K114B Hybrid Powertrain Control Module 2 terminal 48 X2.

• If greater than 2 ohms, repair the open/high resistance in the circuit.

• If less than 2 ohms, replace the K114B Hybrid Powertrain Control Module 2.

• If the test lamp illuminates

4. Vehicle OFF, connect the X1 harness connector at the A4 Hybrid/EV Battery Pack.

5. Perform the High Voltage Disabling procedure before proceeding with this diagnostic. Refer to High Voltage Disabling High Voltage Disabling.

6. Reconnect the 12 V battery.

7. Vehicle OFF, connect EL-50211 low voltage jumper harness extension.

8. Disconnect the X1 harness connector at the K16 Battery Energy Control Module.

9. Vehicle in Service Mode.

10. Verify that a test lamp illuminates between the high voltage energy management communication enable circuit terminal 16 X1 at K16 Battery Energy Control Module and ground.

• If the test lamp does not illuminate
Replace the Drive Motor Battery Wire Junction Block Relay.

• If the test lamp illuminates

11. Replace the K16 Battery Energy Control Module.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the repair.

* Drive Motor Battery Wire Junction Block Relay Replacement Drive Motor Battery Wire Junction Block Relay Replacement

* Control Module References Programming and Relearning for device replacement, programming and setup

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