Battery Junction Box

This procedure covers the removal and replacement of the battery junction box on the 2023 Chevrolet Bolt EUV, which manages high-voltage distribution from the battery pack to vehicle systems.

Warnings

Tools required

Parts

• Battery junction box assembly × 1 — Use OEM specification
• High-voltage connector seals × 1 — Use OEM specification
• Cable ties × 10 — OEM harness ties
• Coolant (if lines disconnected) × 1 — ACDelco DEX-COOL

Preparation

1. Park vehicle on level surface and apply parking brake. Place safety cones around work area.
2. Ensure ignition is OFF and key fob is at least 15 feet away from vehicle.
3. Open hood and locate 12V battery in front compartment. Disconnect 12V negative terminal first, then positive terminal.
4. Allow vehicle to sit for 5 minutes to discharge vehicle control modules.
5. Remove rear seat bottom cushion to access high-voltage service disconnect located in center tunnel.
6. Using insulated tools, remove high-voltage service disconnect plug and store in pocket or toolbox away from vehicle.
7. Wait minimum 15 minutes for high-voltage system capacitors to discharge.
8. Put on high-voltage insulated gloves rated for at least 1000V.
9. Remove front belly pan and underbody panels to access battery pack from below (may require lift).
10. Tag and photograph all electrical connectors and harness routing for proper reassembly.

Procedure

1. 1

   Verify system de-energization
   Using a high-voltage rated digital multimeter, verify that voltage between high-voltage positive and negative bus bars reads 0V DC. Check multiple points throughout the high-voltage system. Do not proceed until voltage reads 0V at all test points. This is a mandatory safety verification step.
   ⚠️If any voltage is detected, do not proceed. Investigate why system has not discharged and verify service disconnect is removed.
2. 2

   Disconnect battery coolant lines
   Locate the coolant lines connected to the battery thermal management system near the junction box. Place drain pan beneath connections. Carefully loosen coolant line fittings and disconnect from battery junction box. Cap or plug open lines immediately to prevent contamination and fluid loss.
   ⚠Coolant may be hot or under pressure even after waiting period. Loosen fittings slowly to relieve any residual pressure.
   Torque spec

   Coolant Line Fittings15 Nm (11 lb-ft)
3. 3

   Remove junction box protective covers
   Remove all protective covers and shields surrounding the battery junction box. These are typically secured with multiple cover screws. Keep covers organized and note their orientation for reinstallation. Inspect covers for any damage or corrosion.
   Torque spec

   Cover Screws11 Nm (8 lb-ft)
4. 4

   Disconnect low-voltage control connectors
   Identify and disconnect all low-voltage control connectors from the battery junction box. These include sensor connectors, communication bus connectors, and control module connectors. Press release tabs and pull connectors straight out. Label each connector with tape and marker if not already tagged.
   Torque spec

   Connector Bolts7 Nm (5 lb-ft)
5. 5

   Disconnect high-voltage input connectors
   Wearing high-voltage insulated gloves, locate the high-voltage input connectors (orange cables) from the battery pack to the junction box. Remove the high-voltage connector bolts securing each connector. Carefully pull connectors straight back to disengage. Inspect connector seals and terminals for damage or corrosion. Store connectors away from work area to prevent contamination.
   ⚠️Even though system is de-energized, treat all orange cables as live. Never allow conductors to contact vehicle chassis or each other.
   Torque spec

   Connector Bolts7 Nm (5 lb-ft)
6. 6

   Disconnect high-voltage output connectors
   Remove the high-voltage connector bolts from the output side of the junction box (cables leading to motor inverter, HVAC compressor, and DC-DC converter). Carefully disconnect each orange cable connector. Note the specific position and routing of each output cable as they must be reconnected to correct terminals.
   Torque spec

   Connector Bolts7 Nm (5 lb-ft)
7. 7

   Disconnect ground connections
   Locate and remove all ground cable connections from the battery junction box. Remove ground cable bolts and carefully set aside ground straps. Clean ground contact surfaces if corrosion is present.
   Torque spec

   Ground Cable Bolt14 Nm (10 lb-ft)
8. 8

   Remove junction box mounting hardware
   Remove all mounting bolts securing the battery junction box to the battery pack assembly or vehicle structure. Support the junction box weight as you remove the final bolts. The junction box may be heavy and awkwardly positioned.
   Torque spec

   Mounting Bolts27 Nm (20 lb-ft)

   Bracket Bolts20 Nm (15 lb-ft)
9. 9

   Remove battery junction box
   Carefully maneuver the battery junction box out of its mounting location. Be mindful of any remaining harness connections or coolant hoses. The junction box may need to be tilted or rotated to clear surrounding components. Place removed junction box on clean, non-conductive work surface for inspection or disposal per local regulations.
10. 10

    Prepare new junction box
    Unpack new battery junction box and verify part number matches vehicle specifications. Inspect all mounting points, connector terminals, and coolant ports for shipping damage. Install new high-voltage connector seals if provided separately. Transfer any sensors or brackets from old junction box if they are not included with replacement unit and are confirmed serviceable.
11. 11

    Install new junction box
    Position new battery junction box into mounting location, carefully routing it past surrounding components. Align mounting holes with battery pack or vehicle structure mounting points. Hand-thread all mounting bolts first to ensure proper alignment before final tightening.
    ℹ️Ensure junction box is fully seated before tightening bolts. Misalignment can cause connector or coolant fitting issues.
    Torque spec

    Mounting Bolts27 Nm (20 lb-ft)

    Bracket Bolts20 Nm (15 lb-ft)
12. 12

    Reconnect ground connections
    Reconnect all ground straps to the battery junction box. Ensure mating surfaces are clean and free of corrosion. Install ground cable bolts and torque to specification. Verify ground straps are not pinched or stressed.
    Torque spec

    Ground Cable Bolt14 Nm (10 lb-ft)
13. 13

    Reconnect high-voltage connectors
    Wearing high-voltage insulated gloves, reconnect all high-voltage input and output connectors to the correct terminals on the junction box. Ensure connectors are fully seated and orange cable seals are properly positioned. Install high-voltage connector bolts and torque to specification in a star pattern if multiple bolts per connector. Verify no wire strands are visible outside connector housings.
    ⚠️Verify each orange connector is attached to correct terminal per service manual wiring diagram. Incorrect connections can cause severe damage when energized.
    Torque spec

    Connector Bolts7 Nm (5 lb-ft)
14. 14

    Reconnect low-voltage connectors
    Reconnect all low-voltage control connectors to the battery junction box. Ensure each connector clicks into place and locking tabs engage. Verify connectors match your labels or photos from disassembly. Install any connector bolts and torque to specification.
    Torque spec

    Connector Bolts7 Nm (5 lb-ft)
15. 15

    Reconnect coolant lines
    Remove caps or plugs from coolant lines. Reconnect coolant lines to battery junction box fittings. Ensure fittings are clean and O-rings are in good condition. Torque coolant line fittings to specification. Check for proper seating and alignment.
    Torque spec

    Coolant Line Fittings15 Nm (11 lb-ft)
16. 16

    Install protective covers
    Reinstall all protective covers and shields over the battery junction box. Ensure no wires or hoses are pinched. Install cover screws and torque to specification. Verify covers are fully seated and properly aligned.
    Torque spec

    Cover Screws11 Nm (8 lb-ft)
17. 17

    Final inspection and system preparation
    Perform final visual inspection of all connections, ensuring all bolts are torqued, all connectors are engaged, and no tools or parts are left in work area. Verify coolant system is properly filled and bled per service manual procedures if coolant was lost. Reinstall all underbody panels and belly pan. Reconnect 12V battery (positive first, then negative).

Reassembly

1. Double-check that all high-voltage connectors are on correct terminals per wiring diagram
2. Verify all protective covers are installed and fasteners are torqued to specification
3. Ensure no harnesses are pinched, stretched, or routed incorrectly
4. Confirm coolant level is correct and system is properly bled if coolant lines were disconnected
5. Verify 12V battery is reconnected with positive terminal first, then negative

Verification

• Before reinstalling high-voltage service disconnect, use scan tool to check for any diagnostic trouble codes
• Verify battery management system communication is established with vehicle network
• Reinstall high-voltage service disconnect plug and verify security
• With vehicle still on lift, power on vehicle to READY mode and verify no warning lights on instrument cluster
• Use scan tool to monitor battery junction box parameters including voltage, current, and temperature sensors
• Perform test drive and verify normal operation of high-voltage systems including propulsion, regenerative braking, and HVAC
• After test drive, inspect junction box area for any coolant leaks, loose connections, or unusual heat
• Clear any stored diagnostic codes that may have set during service and verify no new codes return
• Document junction box replacement with part number, date, and vehicle mileage in service records

Related trouble codes on this vehicle

Codes that commonly send this job to the bay — tap one for symptoms, causes, and diagnostic steps.

Chasing one of these codes and not sure which part is guilty? Ask a master mechanic about YOUR car →

More procedures for this vehicle