EV Thermal Management System

Complete diagnostic, maintenance, and repair procedure for the Rivian EDV 500's integrated thermal management system, which manages cooling for the battery pack, drive units, and power electronics.

Warnings

Tools required

Parts

• Coolant hose O-rings × 1 — Use OEM specification
• Thermal management system coolant filter × 1 — Use OEM specification
• Coolant temperature sensor × 1 — Use OEM specification as needed
• Coolant flow sensor × 1 — Use OEM specification as needed
• Electric coolant pump × 1 — Use OEM specification as needed

Fluids

• EV Battery/Motor Coolant — 10 qt

Preparation

1. Park vehicle on level surface and apply parking brake. Chock rear wheels if raising front of vehicle.
2. Verify vehicle has been off for minimum 2 hours to allow thermal system to cool below 100°F.
3. Access Rivian service mode through center display: Settings > Service > Service Mode. Enter technician credentials.
4. Connect Rivian diagnostic scanner and document all active and stored fault codes related to thermal management.
5. Perform high voltage isolation procedure: Power off vehicle, remove 12V service disconnect located in frunk, wait 5 min for capacitor discharge, verify zero voltage at HV terminals with safety meter.
6. Install high voltage lockout/tagout device on service disconnect and retain key on person.
7. Remove front underbody aero panels to access thermal system components (8 plastic clips and 4 fasteners per panel).
8. Place large drain pan under vehicle centered beneath battery pack cooling plate access.

Procedure

1. 1

   Perform thermal system diagnostic scan
   Using Rivian diagnostic tool, navigate to Thermal Management module. Run complete system test including coolant pump function test, temperature sensor validation, flow rate test, and thermal valve operation test. Record all sensor readings including inlet/outlet temperatures for battery, front drive unit, and rear drive unit. Check for fault codes P1A00-P1AFF range (thermal management specific). Document baseline coolant level in expansion tank.
2. 2

   Visual inspection of thermal system components
   Inspect all visible coolant hoses for cracks, swelling, or leaks, paying special attention to quick-disconnect fittings at battery pack entry points. Check coolant reservoir tank for correct fill level (should be between MIN and MAX marks when cold). Inspect electric coolant pumps (located on driver side frame rail) for coolant seepage at motor housing. Check radiator and chiller unit mounting for damage. Use thermal camera if available to identify hot spots indicating flow restrictions or blockages.
3. 3

   Pressure test the thermal system
   Remove coolant reservoir cap (turn counterclockwise and allow any residual pressure to release slowly). Install coolant pressure tester adapter to reservoir opening. Pressurize system to 15 PSI and hold for 10 minutes. System should not lose more than 1 PSI during test period. If pressure drops, use diagnostic scanner to isolate circuit (battery vs drive unit) by commanding individual coolant pumps. Inspect all connections, hose junctions, and component seals for leaks while under pressure. Pay special attention to battery cooling plate interfaces and drive unit coolant jackets.
4. 4

   Drain coolant from affected circuit
   Release pressure from system completely. Locate drain valve for affected circuit: battery circuit drain is beneath battery pack center access panel, drive unit circuit drain is on low point of front coolant manifold. Attach drain hose to valve and route to drain pan. Open drain valve (turn counterclockwise 2 full turns). For complete drain, use diagnostic tool to pulse coolant pump in 5-second intervals to move fluid from remote areas. Collect and measure drained coolant to verify system capacity. Inspect drained coolant for contamination, metal particles, or discoloration indicating component degradation.
5. 5

   Remove and replace coolant filter element
   Locate thermal system coolant filter housing on driver frame rail forward of front drive unit. Using 22mm socket, rotate filter housing cap counterclockwise to remove. Extract filter element and inspect for debris accumulation. Excessive metal particles indicate bearing wear in coolant pump or drive unit. Replace filter element with new OEM unit. Lubricate O-ring on filter housing cap with fresh coolant before reinstallation. Install cap and rotate clockwise until seated, then an additional 1/8 turn.
6. 6

   Inspect and test coolant temperature sensors
   Using diagnostic scanner, monitor individual temperature sensor readings with ambient reference. Battery inlet, battery outlet, front drive unit, rear drive unit, and chiller sensors should all read within 5°F of each other when cold-soaked. If sensor reading is out of range or shows fault code, access sensor location (varies by circuit), disconnect electrical connector, and measure resistance. At 68°F, sensor should read 2400-2600 Ohms. Replace any sensor outside this range. Apply dielectric grease to connector during reinstallation.
7. 7

   Test electric coolant pump operation
   There are three electric coolant pumps: battery circuit pump, drive unit circuit pump, and HVAC chiller pump. Access each pump electrical connector and verify no corrosion on terminals. Using diagnostic tool, command each pump individually to 100% duty cycle (vehicle must be in service mode). Pump should operate smoothly without grinding or rattling. Measure current draw: normal is 3-6 amps depending on circuit. If pump fails to operate, shows excessive current draw (over 8 amps), or makes abnormal noise, replace pump assembly. Pump replacement requires removing mounting bracket (3 bolts) and disconnecting inlet/outlet quick-connect fittings.
8. 8

   Inspect thermal management valves and actuators
   The system uses electrically-controlled thermal valves to direct coolant flow between battery, drive units, radiator, and chiller based on thermal load. Using diagnostic tool, command each valve through full range of motion and monitor position feedback. Valves are located in thermal management unit behind front bumper cover. Access requires removing lower grille panel. Listen for valve motor operation (should be smooth, not clicking). Check valve body for external coolant leaks at shaft seals. If valve does not reach commanded position within 5 seconds or shows position sensor fault, replace valve assembly.
9. 9

   Clean and inspect thermal interfaces
   If accessing battery cooling plate or drive unit thermal interface, inspect thermal interface material (TIM) condition. TIM should be evenly distributed without dry spots, cracks, or separation. Battery cooling plate channels should be free of corrosion or deposits. If TIM shows degradation, carefully clean old material using lint-free cloth and isopropyl alcohol. Apply new TIM per Rivian specification (typically 0.5mm thick layer). For drive unit thermal interfaces, verify coolant jacket contact with motor housing is even and mounting bolts are present and undamaged.
10. 10

    Replace faulty components as identified
    Based on diagnostic findings, replace any failed components including sensors, pumps, valves, hoses, or seals. Always use OEM-specified parts for thermal system components. When disconnecting coolant quick-connect fittings, press release collar while pulling connector straight off. Inspect O-rings in fitting and replace if any damage visible. For coolant pump replacement, transfer mounting bracket to new pump, apply thread locker to mounting bolts, and torque to hand-tight plus 1/4 turn (no torque spec provided). Ensure all electrical connectors are fully seated with positive click.
11. 11

    Vacuum fill the thermal system
    Close all drain valves. Connect vacuum fill tool to coolant reservoir. Draw vacuum on system to minimum 25 inches Hg and hold for 5 minutes to verify no leaks (vacuum should not drop more than 2 inches). Place fill tool supply hose in container of fresh EV Battery/Motor Coolant. Release vacuum to draw coolant into system. System will take approximately 10 quarts for complete fill depending on circuit serviced. Once coolant visible in reservoir, disconnect vacuum tool. Add coolant to reservoir until level reaches MAX mark. Install reservoir cap.
12. 12

    Bleed air from thermal system
    With vehicle still in service mode and high voltage still isolated, use diagnostic tool to run coolant pump purge procedure. This cycles pumps at varying speeds to purge air pockets. Battery circuit requires 10-minute purge cycle, drive unit circuit requires 15-minute cycle due to higher point cooling passages. Monitor coolant level in reservoir during purge and add coolant as level drops. System is properly bled when no air bubbles visible in reservoir and coolant level remains stable during pump operation.
13. 13

    Restore high voltage and perform system test
    Reinstall all underbody panels and access covers. Verify all thermal system connections secure and no tools left in work area. Remove high voltage lockout device and reinstall 12V service disconnect in frunk. Using diagnostic scanner, clear service mode and all stored fault codes. Power on vehicle and allow thermal management system to initialize (approximately 30 seconds). Monitor all coolant temperature sensors to verify readings are consistent. Command thermal system to test mode and verify all pumps, valves, and sensors respond correctly.
14. 14

    Perform thermal load test
    With vehicle stationary and diagnostic tool connected, command drive units to generate thermal load (vehicle in service mode allows stationary motor operation). Monitor battery and drive unit temperatures as they rise. Verify coolant pumps increase speed as temperature increases. Confirm thermal valves direct flow to radiator when temperature exceeds 130°F. Observe temperature delta between inlet and outlet sensors (should be 10-25°F under load). System should maintain battery below 110°F and drive units below 150°F under continuous load. Any overtemperature conditions indicate flow restrictions or component failures requiring further diagnosis.
15. 15

    Final verification and road test
    Exit service mode and restore vehicle to normal operation. Perform 15-minute test drive including moderate acceleration and regenerative braking to generate thermal load under real conditions. Monitor thermal system operation via vehicle display and diagnostic scanner. After test drive, verify no coolant leaks at any connections or components. Check coolant level in reservoir (should remain at MAX mark). Verify no new fault codes stored. Document all repairs, part numbers, and final coolant level in service records. Provide customer with thermal system performance report.

Reassembly

1. Ensure all coolant hose quick-connect fittings are fully seated with release collars in locked position
2. Verify all electrical connectors to thermal components are secured and connector locks engaged
3. Reinstall underbody aero panels ensuring all clips and fasteners are properly secured to maintain aerodynamic efficiency
4. Torque all removed fasteners to specification when torque values become available in database
5. Verify coolant reservoir cap is installed and fully tightened to maintain system pressure
6. Confirm no tools or materials left in engine bay or under vehicle before final inspection

Verification

• Connect diagnostic scanner and verify no active or pending fault codes in thermal management system
• Confirm all coolant temperature sensors reading within 5°F of each other at ambient temperature
• Verify coolant level in reservoir at MAX mark with system cold
• Check that all three coolant pumps respond to commanded operation via diagnostic tool
• Confirm thermal valves reach commanded positions and provide correct feedback
• Verify no coolant leaks visible at any component or connection point
• Test drive vehicle for minimum 15 minutes and confirm thermal system maintains proper operating temperatures
• Verify battery temperature remains below 110°F and drive units below 150°F under moderate load
• Confirm coolant temperature delta between inlet and outlet sensors is appropriate (10-25°F under load)
• Document all sensor readings, system performance data, and repairs in vehicle service history

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