P0C78
DTC P0C77 or P0C78
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 P0C77
- Hybrid/EV Battery System Precharge Time Too Short
DTC P0C78
- Hybrid/EV Battery System Precharge Time Too Long
DTC P0D5E
- Charger Bus Discharge Too Long
Circuit/System Description
The battery energy control module will diagnose its own systems and determine when a fault condition is present. Diagnostics and system status is communicated from the battery energy control module to the hybrid powertrain control module 2 through serial data. The hybrid powertrain control module 2 is the host controller for diagnostic trouble code (DTC) information.
The hybrid battery contains 5 high voltage contactors and 2 transistors. The high voltage contactors allow the high voltage DC batteries to be connected to the vehicle or safely contain the high voltage DC within the hybrid battery assembly. The 5 high voltage contactors are a main positive high voltage contactor, main negative high voltage contactor, charge positive high voltage contactor, charge negative high voltage contactor, and multi-function high voltage contactor. The 2 transistors are the precharge transistor and heater transistor. These contactors/transistors close and open in sequence and are controlled by the hybrid powertrain control module 2. The hybrid powertrain control module 2 supplies voltage to the control circuit for the high voltage contactors/transistors. Ground is provided through the case ground.
Conditions for Running the DTC
* The system voltage is greater than or equal to 9 V.
* The main contactors are in precharge mode.
* None of the following DTCs are set: P0ABC, P0ABD, P1A07, P0ABB, P0AF8, P1AE8, P1AE9, or P1AEC
Conditions for Setting the DTC
P0C77
The bus voltage is above 80% of battery voltage in less than 50ms.
P0C78
The bus voltage has not reached 95% of battery voltage in 700ms.
P0D5E
INSERT TBD TEXT HERE
Action Taken When the DTC Sets
* DTC P0C77, P0C78, and P0D5E are type A DTCs.
* The contactors will be opened.
Conditions for Clearing the DTC
DTC P0C77, P0C78, and P0D5E are type A DTCs.
Diagnostic Aids
Note: If the high voltage contactors opened while under high current load, replace BOTH high voltage contactors. The following conditions could cause the high voltage contactors to open while under high current load:
* A collision resulting in supplemental inflatable restraint (SIR) deployment.
* A loss of power or ground to the hybrid powertrain control module 2 while the vehicle is moving.
The precharge time can be affected by the following:
* A long precharge time may be caused by an open 125 A fuse in the manual disconnect lever
* A short precharge time may be caused by a positive high voltage contactor stuck.
* A negative high voltage contactor stuck closed will not affect the precharge sequence.
A long or short precharge time may cause any of the following;
The hybrid powertrain control module 2 will start a precharge wait timer after failing 2 consecutive precharge events. The contactors will not close until the precharge wait time has timed out.
Reference Information
Schematic Reference
Hybrid Energy Storage Schematics Hybrid Energy Storage Schematics
Connector End View Reference
Component Connector End Views Hybrid/EV Battery Pack X1 A4
Description and Operation
Drive Motor Battery System Description Drive Motor Battery System Description
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
Special Tools
EL-48900 - HEV Safety Kit
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 will perform the following tasks:
* 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 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 at all times when working with the high voltage battery assembly, whether the system is energized or not.
Failure to follow the procedures exactly as written 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 (1-877-446-8227) if you have any questions.
1. Ignition OFF, disable the high voltage at the T6 power inverter module. Refer to High Voltage Disabling High Voltage Disabling.
2. Test for 35-45 ohm between the following terminals of the S15 manual service disconnect.
* Terminal A and terminal B
* Terminal C and terminal D
• If the test result is not in the specified range, replace the S15 manual service disconnect.
3. Reconnect the S15 manual service disconnect.
4. Connect the 12 V battery.
5. Ignition ON, verify that DTC P0AA1, P0AD9, P0ADD, P0AE2, P0AE4, P0AFA, P0D0A, P0D11, P1EBC-P1EBF, P1EC0, or P1EC3-P1EC5 is not set.
• If any DTC is set, diagnose them first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.
6. With a scan tool, verify the Hybrid Battery Pack Voltage parameter is greater than 205 V at room temperature.
• If the test result is less than the specified value, replace the A4 hybrid battery pack.
7. Ignition OFF, disconnect the X1 harness connector at the A28 hybrid battery contactor assembly.
8. Connect a test lamp between the control circuit terminal 11 and ground.
9. Ignition ON, engine OFF, command the hybrid battery pack precharge transistor command parameter OPEN and CLOSED with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
• If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K114B hybrid powertrain control module 2.
• If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K114B hybrid powertrain control module 2.
10. Ignition OFF, reconnect the X1 harness connector.
11. Remove the fuse cover and battery protector (Insulator). Refer to Battery Charger and 14 V Power Module Maxi 20 A Fuse Replacement Battery Charger and 14 V Power Module Maxi 20 A Fuse Replacement.
12. With a DMM, test for less than 1 ohm across the battery charger fuse.
• If the test result is greater than the specified value, replace the battery charger fuse.
13. With a DMM, test for less than 1 ohm across the 14 V Power Module fuse.
• If the test result is greater than the specified value, replace the 14 V Power Module fuse.
14. Disconnect the X3 harness connector at the A28 hybrid battery contactor assembly.
15. Test for infinite resistance between the harness connector terminal A and terminal B X3 at the T6 power inverter module.
• If the test result is less that the specified value, replace the 300 V cables.
16. Test for infinite resistance between the following terminals and ground.
* Terminal A X3
* Terminal B X3
• If the test result is less that the specified value, replace the 300 V cables.
17. Test for less than 10 ohm between the following 300 V circuits end to end:
* T6 power inverter module terminal A X3 and A28 hybrid battery contactor assembly terminal A X3.
* T6 power inverter module terminal B X3 and A28 hybrid battery contactor assembly terminal B X3.
• If the test result is greater that the specified value, replace the 300 V cables.
18. Ignition OFF, connect a DMM between terminal A and terminal B X3 at the T6 power inverter module.
19. Test for greater than 1 ohm and less than 2M ohm between terminal A and terminal B X3 at the T6 power inverter module.
• If not within the specified range, replace the T6 power inverter module.
20. If all the circuit tests normal, replace the A28 hybrid battery contactor assembly.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Battery Cable Replacement (Terminal to Battery 1) Battery Cable Replacement (Terminal to Battery 1)Battery Cable Replacement (Battery 2 to Battery 3) Battery Cable Replacement (Battery 2 to Battery 3)Battery Cable Replacement (Battery 3 to Battery 4) Battery Cable Replacement (Battery 3 to Battery 4)Battery Cable Replacement (Terminal to Battery 4) Battery Cable Replacement (Terminal to Battery 4)
* 300-Volt Battery Positive and Negative Cable Replacement (Drive Motor Battery-to-Inverter ) 300-Volt Battery Positive and Negative Cable Replacement (Drive Motor Battery-to-Inverter )300-Volt Battery Positive and Negative Cable Replacement (Inverter-to-Compressor/Heater Module) 300-Volt Battery Positive and Negative Cable Replacement (Inverter-to-Compressor/Heater Module)300-Volt Battery Positive and Negative Cable Replacement (Drive Motor Battery-to-APM Module) 300-Volt Battery Positive and Negative Cable Replacement (Drive Motor Battery-to-APM Module)300-Volt Battery Positive and Negative Cable Replacement (Drive Motor Battery-to-Charger) 300-Volt Battery Positive and Negative Cable Replacement (Drive Motor Battery-to-Charger)
* Control Module References Control Module References for drive motor generator battery control module, drive motor generator power inverter module, air conditioning control module assembly replacement, programming and setup