Loss of Isolation on the High Voltage Main Bus
Loss of Isolation on the High Voltage Main Bus
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.
Circuit/System Description
The hybrid system monitors the electrical potential between high voltage and the vehicle chassis. High voltage should always be isolated from the vehicle chassis by a certain amount of resistance to avoid the potential for a life threatening current path. In the event that a high voltage leak path is detected to the vehicle chassis, the hybrid system will set a diagnostic trouble code (DTC). High voltage DC chassis isolation is monitored by the motor control modules and the hybrid powertrain control module 2.
Testing for loss of isolation requires special tools and procedures. Because of the high voltages present in the hybrid system, a loss of isolation may occur due to insulation breakdown. Insulation breakdown typically occurs only when high voltages and/or current is present. Conditions such as insulation breakdown cannot be diagnosed with a typical DMM because high voltage is not used by the DMM when measuring resistance.
The power inverter module, often referred to as the hybrid powertrain control module, contains two motor control modules. Each motor control module measures hybrid battery high voltage with several internal sensors. The motor control modules test for loss of isolation between either the high voltage positive circuit or high voltage negative circuit and vehicle chassis. The motor control modules test for isolation when the high voltage contactor relays are closed. The hybrid powertrain control module 2 only tests the hybrid battery assembly for high voltage loss of isolation when the high voltage contactor relays are open.
Motor control module loss of isolation is detected through the use of two high-impedance resistors and voltage measuring circuitry. The two resistors are connected in series between the high voltage positive and high voltage negative circuits. The center connection of the two resistors is also connected to vehicle chassis. The motor control module then measures the voltage drop across one of the resistors. Without a loss of isolation, the motor control module should measure about half of the high voltage potential. This is referred to as mid-pack voltage. The Mid-pack voltage value is then doubled by the software and displayed on a scan tool as Motor 1 Isolation Voltage or Motor 2 Isolation Voltage. When a loss of isolation is present, the motor isolation voltage display will indicate voltage that is more or less than actual hybrid battery high voltage. The motor control module monitors the loss of isolation voltage measuring circuitry for correct operation.
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
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 Programming and Relearning for scan tool information
Special Tools
* EL-48900 - HEV Safety Kit
* EL-50772 - Insulation Multimeter
For equivalent regional tools, refer to Special Tools Tools and Equipment.
Circuit/System Testing
Danger:
Ensure all High Voltage safety procedures are followed. Failure to follow the procedure exactly as written may result in serious injury or death.
Danger:
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 procedure exactly as written may result in serious injury or death.
Danger:
This vehicle is equipped with a high voltage battery that is completely isolated from the chassis ground. Never utilize AC powered test equipment to probe the high voltage system. Serious injury, death and component damage could occur if the high voltage system is grounded through the electric utility.
Failure to follow the procedure 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 if you have any questions.
Loss of Isolation on the High Voltage Main Bus
1. Vehicle in Service Mode, verify that DTC P0AA1, P0AD9, P0ADD, P0AE2, P0AE4, P0D0A, P0D11, P1EBC-P1EBF, P1EC0, or P1EC3-P1EC5 is not set.
• If any DTC is set, diagnose them first. Refer to DTC P0AA1, P0AD9, P0ADD, P0AE2, P0AE4, P0D0A, P0D11, P1EBC-P1EBF, P1EC0, or P1EC3-P1EC5 P0AA1.
Note: Wear your High Voltage Insulation gloves until you have determined that a high voltage exposure risk is no longer present.
2. Vehicle OFF, disable the high voltage at the A4 hybrid battery pack. Refer to High Voltage Disabling High Voltage Disabling.
Note: The following continuity tests must be performed using the EL-50772 - Insulation Multimeter. Select the Isolation test setting, then select the 500 V range.
3. Using the EL-50772 - Insulation Multimeter test for greater than 750k ohms between the circuit terminals listed below and ground.
* A28 Hybrid battery contactor assembly harness connector terminal A +300 V X4.
* A28 Hybrid battery contactor assembly harness connector terminal B -300 V X4.
• If the test result is less than the specified value, disconnect the X1 connector at the K1 14 V power module. Test for greater than 750k ohms. If the test result is greater than the specified value, replace the K1 14 V power module. If the test result is less than the specified value, replace the 300 V DC cables.
4. Test for greater than 750k ohms between the circuit terminals listed below and ground.
* T6 Power inverter module harness connector terminal 1 -300 V X3.
* T6 Power inverter module harness connector terminal 2 +300 V X3.
• If the test result is less than the specified value, replace the 300 V DC cables.
5. Disconnect the X4 harness connector at the T6 power inverter module.
Note: The following continuity tests require both the air conditioning control module and cabin heater control module circuits to be isolated by performing the following test up to 3 times if a fault is detected.
6. Test for greater than 750k ohms between the circuit terminals listed below and ground.
* Terminal A +300 V X4.
* Terminal B -300 V X4.
• If the test result is less than the specified value, disconnect the X2 connector at the G1 air conditioning control module. Test for greater than 750k ohms between the circuit terminal and ground. If the test result is greater than the specified value, replace the G1 air conditioning control module.
• If the test result is less than the specified value, with the X2 connector at the G1 air conditioning control module disconnected. Disconnect the X2 connector at the K10 cabin heater control module. Test for greater than 750k ohms between the circuit terminal and ground. If the test result is greater than the specified value, replace the K10 cabin heater control module. If the test result is less than the specified value, replace the 300 V DC cables.
7. Disconnect the X5 harness connector at the at the T6 power inverter module
Note: There may be up to a 5 second delay for proper test results to be displayed.
8. Test for greater than 750k ohms between the 3 phase cable circuit terminals listed below and ground.
* Terminal 1 300 V X5.
* Terminal 2 300 V X5.
* Terminal 3 300 V X5.
• If the test result is less than the specified value, disconnect the X2, X3, and X4 connector at the M15A Drive Motor 1. Test for greater than 750k ohms between the circuit terminal and ground. If the test result is greater than the specified value, replace the M15A Drive Motor 1. If the test result is less than the specified value, replace the 3 phase cables.
9. Disconnect the X6 harness connector at the at the T6 power inverter module.
10. Test for greater than 750k ohms between the 3 phase cable circuit terminals listed below and ground.
* Terminal 1 300 V X6.
* Terminal 2 300 V X6.
* Terminal 3 300 V X6.
• If the test result is less than the specified value, disconnect the X3, X4, and X5 connector at the M15B Drive Motor 2. Test for greater than 750k ohms between the circuit terminal and ground. If the test result is greater than the specified value, replace the M15B Drive Motor 2. If the test result is less than the specified value, replace the 3 phase cables.
11. Disconnect the X8 harness connector at the at the power inverter module.
12. Test for greater than 1.0M ohms between the 3 phase cable circuit terminals listed below and ground.
* Terminal 1 300 V X8.
* Terminal 2 300 V X8.
* Terminal 3 300 V X8.
• If the test result is less than the specified value, replace the G5 transmission fluid pump - auxiliary.
13. Test for greater than 750k ohms between the T6 power inverter module circuit terminals listed below and ground.
* Terminal A +300 V X3.
* Terminal B -300 V X3.
* Terminal A +300 V X4.
* Terminal B -300 V X4.
* Terminal 1 300 V X5.
* Terminal 2 300 V X5.
* Terminal 3 300 V X5.
* Terminal 1 300 V X6.
* Terminal 2 300 V X6.
* Terminal 3 300 V X6.
* Terminal 1 300 V X8.
* Terminal 2 300 V X8.
* Terminal 3 300 V X8.
• If the test result is less than the specified value, replace the T6 power inverter module.
14. Remove the Drive Motor Battery Cover. Refer to Drive Motor Battery Cover Replacement Drive Motor Battery Cover Replacement.
15. Disconnect the harness connector at the E54 hybrid/EV battery pack coolant heater.
16. Test for 61-75 ohms between terminal A and terminal B at the E54 hybrid/EV battery pack coolant heater.
• If not within the specified range, verify that the 20 A charger maxi-fuse is not blown. Replace the 20 A charger maxi-fuse if it is blown and the E54 hybrid/EV battery pack coolant heater.
Note: The following continuity tests must be performed using an EL-50772 Insulation Multimeter. Select the Isolation test setting, then select the 500 V range.
18. With the EL-50772, set on the Isolation test setting, test for 550M ohms between the E54 hybrid/EV battery pack coolant heater terminals listed below and battery tray ground:
* Terminal A
* Terminal B
• If less than the specified value, verify that the 20 A charger maxi-fuse is not blown. Replace the 20 A charger maxi-fuse if it is blown and the E54 hybrid/EV battery pack coolant heater.
19. If all circuits test normal and DTC P1AF0, P1AF2, P1AF4-P1AF7, P1B0B, P1B0C, P1B41, P1B42, P1E22, or P1E1B-P1E1F replace the T6 power inverter module. If none of the T6 power inverter module DTCs are set, replace the A4 hybrid battery pack.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Drive Motor Battery Replacement and Shipping Preparation (Volt) Procedures- A4 hybrid/EV battery pack
* 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 (Drive Motor Battery-to-Charger) 300-Volt Battery Positive and Negative Cable Replacement (Drive Motor Battery-to-Charger)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)
* Air Conditioning and Drive Motor Battery Cooling Compressor Replacement Air Conditioning and Drive Motor Battery Cooling Compressor Replacement- G1 air conditioning control module
* Heater Coolant Heater Replacement Heater Coolant Heater Replacement- K10 cabin heater control module
* Accessory DC Power Control Module Replacement Accessory DC Power Control Module Replacement- K1 14 V power module
* Drive Motor Generator Rotor and Stator Removal - Unit A Drive Motor Generator Rotor and Stator Removal - Unit A- M15A Drive Motor 1
* Drive Motor Generator Rotor, Stator, and Output Sun Gear Shaft Removal - Unit B Drive Motor Generator Rotor, Stator, and Output Sun Gear Shaft Removal - Unit B- M15B Drive Motor 2
* Auxiliary Fluid Pump Motor and Fluid Pump Disassemble Auxiliary Fluid Pump Motor and Fluid Pump Disassemble- G5 transmission fluid pump - auxiliary
* Battery Heater Replacement Battery Heater Replacement - E54 hybrid/EV battery pack coolant heater
* Control Module References Programming and Relearning for the T6 power inverter module replacement, programming and setup