High Voltage Wiring Harness

Complete removal and installation of the high-voltage wiring harness that connects the battery pack to the drive unit and charging system on the 2023 Chevrolet Bolt EUV electric vehicle.

Warnings

Tools required

Parts

• High-voltage wiring harness assembly × 1 — Use OEM specification - GM part number specific to 65kWh FWD variant
• High-voltage connector seals (if damaged) × 1 — Use OEM specification
• Cable retention clips × 1 — Use OEM specification

Preparation

1. Park vehicle on level surface and engage parking brake.
2. Ensure vehicle has been powered off for minimum 5 minutes before beginning work.
3. Chock rear wheels if raising front of vehicle.
4. Open hood and locate 12V battery in engine compartment.
5. Disconnect 12V negative battery cable and isolate from terminal.
6. Wait 2 minutes for vehicle systems to fully power down.
7. Put on Class 0 insulated high-voltage gloves before proceeding.
8. Locate high-voltage service disconnect under rear seat - remove rear seat bottom cushion.
9. Remove service disconnect cover by rotating counterclockwise.
10. Pull high-voltage service disconnect plug straight out and store in a secure location away from vehicle.
11. Install service plug lock-out device or tag to prevent accidental reconnection.
12. Wait minimum 10 minutes for high-voltage system capacitors to discharge.
13. Raise vehicle on lift or jack stands to access underbody components.
14. Remove front belly pan and driver side underbody shield to access harness routing.

Procedure

1. 1

   Verify high-voltage system de-energization
   Using a CAT III rated multimeter set to DC voltage (minimum 1000V range), verify zero voltage between high-voltage positive and negative terminals at the battery pack. Measure at multiple accessible high-voltage connection points. Voltage must read below 5V DC before proceeding. If voltage is present, wait additional time and investigate why system has not discharged.
   ⚠️Do not proceed if ANY voltage above 5V DC is detected. System may not be properly de-energized.
2. 2

   Document harness routing and connections
   Take photographs of the high-voltage harness routing from battery pack to drive unit, including all clips, brackets, and cable management points. Document connector orientation at battery pack, drive unit, onboard charger, and any junction boxes. Note positions of any protective covers or shields. This documentation is critical for proper reinstallation.
   ℹ️Improper routing can cause harness contact with moving parts or hot surfaces, leading to system failure.
3. 3

   Remove interior high-voltage harness covers
   Remove the rear seat assembly completely. Remove trim panels along driver side sill plate to expose high-voltage harness routing from rear battery to front drive unit. Remove protective cover over high-voltage junction box (if equipped). Use plastic trim tools to avoid damaging clips. Label any disconnected low-voltage connectors for reassembly.
   Torque spec

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

   Disconnect battery pack high-voltage connectors
   Locate the main high-voltage positive and negative connectors at the battery pack (typically under rear seat area). Remove protective covers from connectors. Using appropriate socket, loosen and remove high-voltage connector bolts in the following sequence: negative first, then positive. Carefully pull connectors straight back - do not twist or rock. Inspect connector seals for damage and cap connectors with protective covers.
   ⚠Always disconnect negative before positive to minimize arc flash risk if system is not fully de-energized.
   Torque spec

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

   Disconnect onboard charger high-voltage connections
   Locate onboard charger module in front compartment (driver side near headlight area). Remove protective shield over charger connections. Disconnect high-voltage input connectors from charger module by removing connector bolts. Disconnect any additional connectors to auxiliary systems (DC-DC converter, cabin heater if equipped). Cap all disconnected high-voltage connectors immediately.
   Torque spec

   Connector Bolts7 Nm (5 lb-ft)

   Module Mounting Bolts8 Nm (6 lb-ft)
6. 6

   Disconnect drive unit high-voltage connectors
   From underneath vehicle, locate the drive unit (electric motor/transaxle assembly). Remove protective cover over high-voltage connection point. Disconnect three-phase AC high-voltage connectors from drive unit by removing connector bolts. Note connector positions - they are not interchangeable. Support connectors to prevent strain on cables. Cap connectors with protective covers.
   ⚠Three-phase connectors are phase-specific. Mark each connector position before removal.
   Torque spec

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

   Release harness from mounting brackets and clips
   Working from battery to drive unit, release high-voltage harness from all mounting brackets and cable management clips. Remove bracket bolts where harness is secured to body structure. Cut any cable ties (will be replaced during installation). Keep track of all mounting hardware and clip locations. Support harness weight as clips are released to prevent dropping harness.
   Torque spec

   Bracket Bolts20 Nm (15 lb-ft)
8. 8

   Remove high-voltage junction box (if equipped)
   If vehicle is equipped with high-voltage junction box, remove mounting bolts securing box to body. Disconnect any remaining high-voltage and low-voltage connectors. Remove junction box with harness attached. Handle carefully to avoid damaging internal contactors or fuses.
   ⚠Junction box contains high-voltage contactors and fuses. Do not disassemble or attempt to service internal components.
   Torque spec

   Module Mounting Bolts8 Nm (6 lb-ft)
9. 9

   Remove complete harness assembly
   With all connections and mounting points released, carefully remove the complete high-voltage harness assembly from vehicle. Work with a helper due to harness length and weight. Route harness through body openings carefully to avoid snagging on sheet metal. Inspect removed harness for any signs of damage, contamination, or burns. Store removed harness away from work area.
   ℹ️Harness weighs approximately 15-20 lbs and is 12+ feet long. Assistant recommended for removal.
10. 10

    Inspect all connection points and clean contact surfaces
    Inspect high-voltage connector receptacles at battery pack, drive unit, and charger for any signs of corrosion, burns, or contamination. Clean contact surfaces with approved electrical contact cleaner only if necessary. Verify all seals and o-rings in receptacles are intact. Replace any damaged seals before installing new harness. Do not use compressed air on high-voltage contacts.
    ⚠Do not touch connector pins with bare hands. Skin oils can cause resistance and arcing.
11. 11

    Route new high-voltage harness
    Unpack new high-voltage harness and inspect for shipping damage. Reference photos taken during disassembly and route new harness through vehicle following exact original path. Ensure harness maintains minimum 2-inch clearance from exhaust components, suspension travel paths, and sharp edges. Feed harness through grommets and body openings. Do not allow harness to contact moving parts or pinch points.
    ⚠Verify harness routing matches OEM specifications exactly. Incorrect routing can cause chafing and insulation failure.
12. 12

    Install harness mounting brackets and secure routing
    Install all harness mounting brackets to body structure and secure with bracket bolts torqued to specification. Install harness into all cable management clips following original positions. Use new cable ties to secure harness at specified locations. Ensure harness has no tight bends (minimum 6-inch radius) and is not under tension between mounting points. Verify adequate slack for suspension movement and thermal expansion.
    Torque spec

    Bracket Bolts20 Nm (15 lb-ft)
13. 13

    Connect drive unit high-voltage connectors
    Apply thin film of dielectric grease to connector seals (not contact surfaces). Align three-phase connectors to drive unit in correct positions per documentation. Push connectors straight onto terminals until fully seated - verify positive engagement. Install connector bolts and torque to specification in star pattern. Install protective cover over connection area and secure.
    ⚠Do not apply dielectric grease to contact pins or surfaces - only to seals.
    Torque spec

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

    Connect onboard charger high-voltage connectors
    Apply dielectric grease to connector seals. Connect high-voltage connectors to onboard charger module, ensuring proper orientation. Push connectors fully onto terminals until positive engagement. Install connector bolts and torque to specification. Reconnect any auxiliary system connectors (DC-DC converter, cabin heater). Install protective shield over charger connections and secure.
    Torque spec

    Connector Bolts7 Nm (5 lb-ft)

    Module Mounting Bolts8 Nm (6 lb-ft)
15. 15

    Connect battery pack high-voltage connectors
    Apply dielectric grease to connector seals. Connect positive high-voltage connector to battery pack first, pushing straight onto terminal until fully seated. Install connector bolt and torque to specification. Connect negative high-voltage connector and torque bolt to specification. Verify both connections are fully seated with no gaps. Install protective covers over connections.
    ℹ️Install positive connection before negative when reconnecting (opposite of disconnection sequence).
    Torque spec

    Connector Bolts7 Nm (5 lb-ft)

Reassembly

1. Reinstall high-voltage junction box (if equipped) and secure with mounting bolts to specification.
2. Reinstall all interior trim panels, ensuring no wiring is pinched behind panels.
3. Reinstall rear seat assembly and verify proper fit.
4. Reinstall underbody shields and belly pan, verifying no interference with harness.
5. Lower vehicle to ground and remove from lift/jack stands.
6. Perform final visual inspection of all high-voltage connections and harness routing.
7. Verify high-voltage service disconnect plug is still removed and secured away from vehicle.
8. Reconnect 12V negative battery cable to 12V battery.
9. Do not install high-voltage service disconnect yet - verification must be performed first.

Verification

• With high-voltage service disconnect still removed, turn on vehicle to accessory mode and check for any warning lights or fault codes using GM diagnostic tool.
• Connect GM SPS software and verify high-voltage system shows all connections detected (system will show de-energized status).
• Verify no high-voltage insulation fault codes are present.
• Perform high-voltage insulation resistance test using appropriate megohmmeter (minimum 500V test voltage) per GM service procedures - resistance must exceed 100 ohms per volt of pack voltage.
• If insulation test passes, install high-voltage service disconnect plug by pushing straight in until it clicks and locks.
• Rotate service disconnect cover clockwise to secure.
• Turn vehicle to READY mode - verify READY indicator illuminates and no warning lights are present.
• Using scan tool, command high-voltage contactors closed and verify battery voltage appears at drive unit (approximately 350-400V DC).
• Verify cooling system for high-voltage components activates when commanded.
• Perform test drive at low speed (under 25 mph in safe area) to verify drive unit responds normally with no unusual noises or vibrations.
• After test drive, use thermal imaging camera (if available) to inspect all high-voltage connections for even temperature distribution - no hot spots should be present.
• Clear any temporary fault codes and verify no codes return.
• Reinstall rear seat bottom cushion and service disconnect cover.
• Provide customer with documentation that high-voltage system service was performed and system integrity was verified.

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