Pyrotechnic Fuse Inspection

Inspection of high-voltage pyrotechnic fuses in the battery disconnect system to verify proper condition, connection integrity, and absence of deployment indicators.

Warnings

Tools required

Parts

• Pyrotechnic fuse assembly × 1 — Use OEM specification - replace only if deployed or damaged
• High-voltage connector seals × 2 — Use OEM specification
• Cable tie set × 1 — High-voltage rated

Preparation

1. Park vehicle on level surface and apply parking brake
2. Place safety cones or barriers around work area to prevent unauthorized access
3. Ensure fire extinguisher is within immediate reach
4. Verify high-voltage insulated gloves are in good condition with no tears or damage, test per manufacturer specifications
5. Disconnect 12V low-voltage battery negative terminal and wait 2 minutes
6. Access vehicle settings via center display and initiate HV system shutdown if vehicle is operable
7. Remove front trunk (frunk) liner and access panels to expose HV battery compartment
8. Allow minimum 15 minutes for high-voltage capacitor discharge after system shutdown
9. Connect diagnostic tool and verify HV system is de-energized and safe to service

Procedure

1. 1

   Verify High-Voltage System De-Energization
   Using the Rivian diagnostic tool, confirm that the high-voltage system status shows 'Safe to Service' or equivalent indication. Verify that all HV contactor status indicators show 'Open'. Check that HV bus voltage reads less than 5V DC. Document voltage readings and system status.
2. 2

   Don High-Voltage Safety Equipment
   Put on high-voltage insulated gloves rated for minimum 1000V. Verify gloves are properly seated and cover wrists completely. Use insulated tools exclusively for all subsequent steps. Maintain awareness of hand placement at all times.
3. 3

   Access Pyrotechnic Fuse Location
   Locate the pyrotechnic fuse assembly at the main HV battery disconnect point, typically positioned at the front of the battery pack near the main positive and negative bus bars. Remove the protective cover over the HV junction area by releasing retaining clips. The pyrofuse is identifiable by its cylindrical orange housing with warning labels.
4. 4

   Perform Visual Inspection
   Inspect the pyrotechnic fuse housing for any signs of deployment including bulging, discoloration, burn marks, or broken seals. Check the indicator pin or flag (if equipped) - a protruding indicator means the fuse has deployed. Examine all HV cable connections to the fuse for corrosion, heat damage, or looseness. Look for any fluid ingress or contamination around the assembly. Take photos for documentation.
5. 5

   Check Connector Integrity
   Inspect the connector body and pins for damage, corrosion, or signs of arcing. Verify that the locking mechanism is intact and properly engaged. Check that orange high-voltage connector safety locks are in place and undamaged. Examine cable routing for any chafing, pinching, or damage to insulation.
6. 6

   Inspect Mounting and Securing
   Verify that the pyrotechnic fuse assembly is securely mounted to its bracket with no movement or looseness. Check all mounting hardware for proper torque feel (do not loosen unless diagnostic tool confirms safe). Ensure cable management clips and ties are intact and cables are properly routed without stress on connections.
7. 7

   Test Deployment Circuit Continuity
   Using the diagnostic tool, perform a circuit continuity test on the pyrotechnic fuse deployment circuit without deploying the fuse. The tool will verify electrical continuity of the firing circuit while keeping current below deployment threshold. Check that resistance values fall within specification (typically 1.5-3.5 ohms). Record all readings.
8. 8

   Verify Isolation Monitoring System
   Use the diagnostic tool to check the isolation monitoring system status. Verify that HV system isolation resistance is within specification (typically greater than 100 ohms per volt, or >40 megohms for 400V system). Check for any stored fault codes related to isolation faults or pyrofuse circuits.
9. 9

   Inspect Associated Safety Systems
   Check the crash sensor connections and wiring harness that interface with the pyrotechnic fuse deployment system. Verify inertial measurement unit (IMU) connector is secure. Inspect the HV interlock loop continuity - the orange safety plug near the service disconnect should be properly seated.
10. 10

    Document Inspection Findings
    Record all inspection findings in the diagnostic tool or service records including visual condition, electrical test results, isolation resistance values, and any fault codes. Note the pyrofuse part number and manufacturing date from the label. Document that the fuse is NOT deployed and is in serviceable condition. If any abnormalities were found, flag for engineering review before returning to service.
11. 11

    Reinstall Protective Covers
    Replace the protective cover over the HV junction area, ensuring all retaining clips are fully engaged. Verify that no tools or foreign objects remain in the HV compartment. Ensure all HV warning labels are visible and legible.
12. 12

    Clear Inspection Mode
    Using the diagnostic tool, exit service mode and clear any inspection-related temporary codes. Verify the system is ready for re-energization. Do not command HV system activation yet - this will occur during verification phase.

Reassembly

1. Reinstall frunk liner and access panels, ensuring all clips and fasteners are secure
2. Reconnect 12V low-voltage battery negative terminal
3. Remove high-voltage safety equipment only after confirming all HV covers are reinstalled
4. Remove safety barriers from work area

Verification

• Power up the vehicle and verify no new fault codes are present using diagnostic tool
• Confirm HV system energizes normally and ready-to-drive status is achieved
• Check that HV battery voltage and isolation resistance display normal values in diagnostic tool
• Verify no warning messages appear on instrument cluster related to HV system or battery safety
• Perform a short test drive if permitted by inspection findings to confirm normal vehicle operation
• Document completion of pyrotechnic fuse inspection with all test results and clear status

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