DC-DC Converter

This procedure covers the removal and replacement of the DC-DC converter on a 2023 Chevrolet Bolt EUV, which converts high-voltage battery power to 12V for vehicle accessories.

Warnings

Tools required

Parts

• DC-DC Converter Assembly × 1 — GM 42724895 or equivalent
• High-voltage connector seal × 2 — Use OEM specification
• Coolant line O-rings × 2 — Use OEM specification
• Thermal paste (high-voltage grade) × 1 — GM 12378416 or equivalent

Fluids

• ACDelco DEX-COOL (Orange) — 2 qt

Preparation

1. Park vehicle on level surface and apply parking brake
2. Ensure ignition has been off for minimum 2 hours to allow high-voltage system to cool
3. Place high-voltage warning signs on steering wheel and charge port
4. Verify scan tool can communicate with battery management system
5. Document any existing fault codes related to DC-DC converter or 12V system
6. Ensure replacement DC-DC converter part number matches original unit
7. Position coolant drain pan under vehicle beneath DC-DC converter location

Procedure

1. 1

   Disconnect 12V battery
   Open hood and locate 12V battery in engine compartment. Disconnect negative terminal first, then positive terminal. Isolate cables away from battery posts. Wait minimum 2 minutes for vehicle systems to power down completely.
2. 2

   Remove high-voltage service disconnect
   Locate high-voltage service disconnect plug on top of battery pack (accessed from rear seat area or rear cargo). Remove cover by turning counterclockwise. Pull service disconnect plug straight up and out. Install lockout/tagout device. Wait minimum 10 minutes before proceeding to next step.
   ⚠️This is the primary high-voltage disconnect point. Ensure plug is fully removed and locked out before proceeding.
3. 3

   Verify high-voltage system is de-energized
   Don high-voltage insulated gloves. Using high-voltage capable multimeter, verify zero voltage at DC-DC converter high-voltage input terminals (orange cables). Check voltage between both positive and negative terminals, and each terminal to vehicle ground. All readings must be below 3 volts DC. Document voltage readings.
   ⚠️If any voltage above 3V DC is detected, stop work immediately and investigate. System may not be fully discharged.
4. 4

   Drain DC-DC converter coolant
   Locate coolant supply and return lines at DC-DC converter (mounted near front of battery pack). Place drain pan directly below fittings. Slowly loosen coolant line fittings to relieve any residual pressure. Once pressure is relieved, fully disconnect both coolant lines and allow coolant to drain into pan. Cap or plug open coolant lines to prevent contamination.
   Torque spec

   Coolant Line Fittings15 Nm (11 lb-ft)
5. 5

   Remove DC-DC converter access covers
   Remove any underbody panels or trim pieces blocking access to DC-DC converter. This typically includes front portion of battery pack underbody shield. Remove all cover screws and carefully lower panels. Set aside in organized manner with fasteners.
   Torque spec

   Cover Screws11 Nm (8 lb-ft)
6. 6

   Disconnect high-voltage cables
   Wearing high-voltage gloves, locate high-voltage positive and negative cables connected to DC-DC converter input terminals (orange cables with orange connectors). Remove connector bolts from each high-voltage connector. Carefully pull connectors straight off terminals. Inspect connector seals for damage and replace if worn. Secure cables away from work area.
   ⚠Even though system is de-energized, treat all orange cables as if energized. Never allow high-voltage cables to contact vehicle ground or each other.
   Torque spec

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

   Disconnect 12V output harness
   Locate 12V output cable from DC-DC converter (typically black or red cable with standard automotive connector). Remove connector bolt securing 12V power cable to converter output terminal. Disconnect any signal/communication harness connectors from DC-DC converter control module. Label all connectors for proper reassembly.
   Torque spec

   Connector Bolts7 Nm (5 lb-ft)
8. 8

   Remove DC-DC converter mounting hardware
   Identify all mounting bolts securing DC-DC converter to battery pack or chassis. Typically there are 3-4 mounting bolts and 2 bracket bolts. Support DC-DC converter from below to prevent dropping. Remove bracket bolts first, then mounting bolts. Note orientation and position of any ground straps or brackets.
   Torque spec

   Mounting Bolts27 Nm (20 lb-ft)

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

   Remove DC-DC converter assembly
   With all fasteners and connections removed, carefully lower DC-DC converter assembly from vehicle. Unit weighs approximately 15-20 lbs. Tilt and maneuver as necessary to clear surrounding components. Inspect mounting location for any coolant leaks, debris, or damage. Clean mounting surface thoroughly.
10. 10

    Prepare new DC-DC converter
    Remove new DC-DC converter from packaging. Verify part number matches original unit exactly. Inspect all mounting points, terminals, and coolant ports. Apply thin layer of thermal paste to mounting interface surfaces where converter contacts battery pack cooling plate. Install new coolant line O-rings on converter ports.
11. 11

    Install new DC-DC converter
    Position new DC-DC converter into mounting location, ensuring proper alignment with coolant ports and mounting holes. Thread all mounting bolts and bracket bolts by hand first to ensure proper thread engagement. Support converter to prevent stress on partially-installed hardware.
12. 12

    Torque mounting hardware
    Torque all mounting bolts to specification in a crossing pattern to ensure even seating of converter against cooling plate. Follow with bracket bolts. Ensure converter is fully seated with no gaps at thermal interface.
    Torque spec

    Mounting Bolts27 Nm (20 lb-ft)

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

    Reconnect electrical connections
    Install new high-voltage connector seals on both positive and negative connectors. Connect 12V output cable to converter output terminal and torque connector bolt. Reconnect all signal/communication harness connectors. Install high-voltage positive and negative connectors to input terminals, ensuring full engagement. Install and torque high-voltage connector bolts to specification.
    ⚠Verify high-voltage connectors are fully seated before installing bolts. Partial connection can cause arcing when system is energized.
    Torque spec

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

    Reconnect coolant lines
    Connect coolant supply and return lines to DC-DC converter ports, ensuring O-rings remain properly seated. Hand-tighten fittings first, then torque to specification using torque wrench. Double-check both connections for proper engagement.
    Torque spec

    Coolant Line Fittings15 Nm (11 lb-ft)
15. 15

    Reinstall access covers and refill coolant
    Reinstall all underbody panels and trim pieces removed for access. Torque all cover screws to specification. Refill cooling system with ACDelco DEX-COOL coolant through fill port. Use vacuum refill tool if available to ensure complete fill and eliminate air pockets. Fill to proper level per service manual specifications.
    Torque spec

    Cover Screws11 Nm (8 lb-ft)
16. 16

    Reconnect high-voltage system and 12V battery
    Remove lockout/tagout device from high-voltage service disconnect location. Reinstall high-voltage service disconnect plug by inserting straight down until fully seated. Rotate cover clockwise to lock. Reconnect 12V battery, positive terminal first, then negative terminal.
17. 17

    Perform system initialization and verification
    Connect scan tool and clear any stored fault codes related to DC-DC converter replacement. Perform DC-DC converter initialization/programming procedure per manufacturer instructions. Command DC-DC converter on and verify 12V output voltage is 13.5-14.5 volts. Monitor for fault codes. Verify cooling system has no leaks and is at proper level after converter operates.
    ⚠DC-DC converter may require specific programming or calibration procedure through scan tool. Consult service information for your specific model year.

Reassembly

1. Ensure all high-voltage connectors are torqued to specification with new seals installed
2. Verify coolant system is filled to proper level and fully bled of air
3. Confirm all underbody panels are reinstalled and secured
4. Remove all high-voltage warning signs from vehicle

Verification

• With vehicle in Ready mode, verify 12V system voltage is 13.5-14.5 volts using multimeter
• Check for any fault codes related to DC-DC converter, high-voltage system, or 12V charging system
• Verify cooling system shows no leaks after 10 minutes of operation
• Monitor DC-DC converter temperature using scan tool - should not exceed normal operating range
• Test all 12V accessories (headlights, radio, climate control) to confirm proper operation
• Perform test drive and verify no warning lights or messages appear on instrument cluster
• Re-check coolant level after vehicle reaches operating temperature and top off if necessary

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