P1B3F
DTC P1B3F or P1B40
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 P1B3F
- High Voltage System Interlock Circuit 2 Low Voltage
DTC P1B40
- High Voltage System Interlock Circuit 2 High Voltage
Circuit/System Description
The high voltage interlock circuits are utilized to verify high voltage component integrity. The high voltage interlock circuits are two circuit loops that passes through certain high voltage components. The high voltage interlock circuits are used to determine if access to high voltage components is being attempted. The opening of these high voltage components causes high voltage interlock circuit to open. The starter/generator control module monitors both the high voltage interlock 5 V reference circuit voltage and the high voltage interlock signal circuit voltage in order to detect circuit faults. When the starter/generator control module detects a loss of high voltage interlock circuit voltage, the high voltage contactors are commanded open.
The service cover for the starter/generator and the service cover for the hybrid/EV battery pack each contain a high voltage interlock switch. When either cover is removed, the stater/generator control module will respond by opening the high voltage contacts. The 5 V reference circuits and signal circuits for each of the two high voltage interlock loops are completely separate from one another and are monitored as two separate loops, with each setting a specific DTC to indicate a circuit fault. The 5 V reference circuit that feeds the high voltage interlock switch on the starter/generator also supplies the 5 V reference to the brake pedal position sensor.
Conditions for Running the DTC
The starter/generator control module is awake and communicating
Conditions for Setting the DTC
DTC P1B3F
Voltage on the high voltage interlock signal circuit is less than 0.5 V
DTC P1B40
Voltage on the high voltage interlock signal circuit is grater than 4.5 V
Action Taken When the DTC Sets
DTCs P1B3F and P1B40 are type B DTCs
Conditions for Clearing the DTC
DTCs P1B3F and P1B40 are type B DTCs
Diagnostic Aids
* When a circuit fault is detected on the high voltage interlock loop that feeds the starter/generator and the vehicle hood is opened, the starter/generator control module will respond by turning off inverter switching. This will prevent the starter/generator from charging the hybrid/EV battery pack and supplying voltage to the starter/generator control module 12 V output. Operating in this manner will cause an eventual discharge of both the high voltage battery pack and the 12 V battery.
* Because the 5 V reference circuit also supplies voltage to the brake pedal position sensor, a circuit fault on the high voltage interlock loop that feeds the starter/generator will also cause hybrid functions that rely on the brake pedal position, such as auto-stop and regenerative braking, to be disabled.
Reference Information
Schematic Reference
Hybrid Energy Storage Schematics [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Connector End Views By Name
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
For equivalent regional tools, refer to Special Tools Tools and Equipment.
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 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 exactly as written may result in serious injury or death.
Danger: The eAssist battery pack assembly will utilize an exchange program. Please consult the most recent revision of bulletin/PI #PIPXXYYZZ, available in Service Information (SI), for a list of approved eAssist battery pack assembly service procedures. Components that may be removed and serviced without exchanging the complete battery pack assembly 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 high voltage at the A4 hybrid/EV battery pack. Refer to High Voltage Disabling High Voltage Disabling.
2. Disconnect the X1 harness connector at the A15 starter/generator.
3. Connect the 12 V battery.
4. Ignition ON, test for 4.8-5.0 V between the 5 V reference circuit terminal 12 and ground.
• If greater than the specified range, test the 5 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the starter/generator control module.
• If less than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the K59 starter/generator control module.
5. Verify DTC P1B3F is set as current.
• If the DTC is not set, test the signal circuit terminal 11 for a short to voltage. If the circuit tests normal, replace the K59 starter/generator control module.
6. Install a 5 A fused jumper wire between the 5 V reference circuit terminal 12 and the signal circuit terminal 11.
7. Verify DTC P1B40 is set as current.
• If the DTC is not set, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K59 starter/generator control module.
8. If all circuit test normal, replace the A15 starter/generator.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Generator Control Module Replacement Generator Control Module Replacement
* Control Module References Control Module References for starter/generator control module replacement, programming, and setup