Replace the coolant temperature sensor on the electric drive motor cooling system to restore accurate temperature monitoring and prevent overheating protection faults.

Warnings

Tools required

Parts

• Coolant temperature sensor × 1 — Use OEM Rivian specification
• Coolant temperature sensor O-ring × 1 — Use OEM specification
• Underbody panel fasteners (as needed) × 5 — Use OEM specification

Fluids

• EV Battery/Motor Coolant — 2 qt

Preparation

1. Park vehicle on level ground and engage parking brake
2. Ensure vehicle has been off for at least 2 hours to allow cooling system to depressurize and cool
3. Disconnect 12V battery negative terminal (located in front trunk compartment) and wait 5 minutes
4. Raise vehicle using approved lift points and support on jack stands rated for vehicle weight
5. Remove underbody aerodynamic panels to access motor cooling system components (typically 8-12 fasteners)
6. Place coolant drain pan beneath drive unit cooling system
7. Connect diagnostic scanner to verify fault codes related to coolant temperature sensor before beginning repair

Procedure

1. 1

   Locate coolant temperature sensor
   The coolant temperature sensor is mounted on the drive motor coolant outlet pipe, accessible from underneath the vehicle near the front or rear drive unit (depending on which sensor has failed). Identify the sensor by following the coolant hose from the drive unit to the small cylindrical sensor with a 2-pin electrical connector. Clean the surrounding area with shop towels to prevent contamination.
2. 2

   Depressurize cooling system
   Slowly loosen the coolant reservoir cap (located in service area under hood) by turning it counterclockwise one full turn, then pause to allow any remaining pressure to escape. Wait 30 seconds, then remove the cap completely. Verify no coolant spray occurs, confirming the system is fully depressurized.
3. 3

   Drain coolant from sensor area
   Position drain pan directly under the coolant temperature sensor location. Locate the nearest coolant drain point on the drive unit cooling circuit (typically a drain plug or hose connection point below the sensor). Open the drain and allow approximately 1-2 quarts of coolant to drain until the level drops below the sensor mounting point. If no dedicated drain exists, proceed to remove the sensor and allow coolant to drain from the opening.
4. 4

   Disconnect sensor electrical connector
   Locate the 2-pin electrical connector on the coolant temperature sensor. Depress the locking tab and carefully pull the connector straight away from the sensor body. Inspect the connector pins for corrosion or damage. If connector shows signs of coolant intrusion, note this for potential wiring harness service.
5. 5

   Remove old coolant temperature sensor
   Using an appropriate wrench or deep socket (typically 19mm or 22mm depending on sensor design), carefully unthread the coolant temperature sensor from the coolant pipe. Turn counterclockwise while supporting the coolant pipe to prevent stress on connections. Once loose, remove the sensor by hand and immediately position drain pan to catch any additional coolant drainage. Place old sensor in a clean area for comparison with replacement part.
6. 6

   Inspect sensor mounting location
   Examine the threaded bore in the coolant pipe where the sensor was installed. Look for any debris, corrosion, or thread damage. Clean the threads using a wire brush or lint-free shop towel. Inspect the sealing surface for scratches or gouges that could prevent proper seal. If threads are damaged, the coolant pipe may require replacement.
7. 7

   Prepare new sensor for installation
   Remove the new coolant temperature sensor from packaging and verify it matches the original part exactly (connector type, thread size, probe length). Install the new O-ring onto the sensor body if provided separately, ensuring it seats properly in the groove. Do not use any thread sealant or pipe dope unless specifically required by Rivian service documentation, as the O-ring provides the seal.
8. 8

   Install new coolant temperature sensor
   Thread the new sensor into the coolant pipe by hand, turning clockwise until finger-tight. Ensure the sensor threads in smoothly without resistance. Once hand-tight, use a torque wrench to tighten the sensor. Without a manufacturer-specified torque value, tighten to approximately 12-15 lb-ft, or until the O-ring just makes contact and compresses slightly. Over-tightening can damage the sensor or coolant pipe threads.
9. 9

   Reconnect electrical connector
   Align the electrical connector with the pins on the new coolant temperature sensor, ensuring correct orientation. Push the connector firmly onto the sensor until the locking tab clicks into place. Gently pull on the connector to verify it is securely latched. Inspect the connector seal to ensure it is properly seated to prevent moisture intrusion.
10. 10

    Close coolant drain and refill system
    If a drain plug was opened, reinstall and tighten securely. Refill the cooling system through the coolant reservoir with EV Battery/Motor Coolant to the FULL mark. Add coolant slowly to allow air to escape. Capacity for top-off should be approximately 1-2 quarts depending on amount drained. Use only the specified EV coolant; do not mix with standard automotive coolant.
11. 11

    Bleed air from cooling system
    With the coolant reservoir cap still removed, reconnect the 12V battery. Access the vehicle diagnostic system through the center screen or service mode to activate the coolant pump for purging. Run the pump for 2-3 minutes while monitoring coolant level in the reservoir. Add coolant as needed to maintain proper level. Air bubbles should gradually diminish. If bleeding function is not accessible, proceed to next step and allow system to self-bleed during operation.
12. 12

    Reinstall underbody panels
    Verify all tools and drain pans are removed from under the vehicle. Reinstall all underbody aerodynamic panels using original or replacement fasteners. Ensure all panels are properly aligned and seated. Verify no coolant hoses or wiring is pinched or interfering with panel installation.
13. 13

    Clear diagnostic codes
    Using the Rivian diagnostic scanner or OBDII tool, clear all stored fault codes related to the coolant temperature sensor. Record any other codes present for future reference. Exit diagnostic mode.

Reassembly

1. Ensure coolant reservoir is filled to proper FULL level after system has stabilized
2. Verify all electrical connectors are fully seated and locked
3. Confirm all underbody panels are securely fastened and aligned
4. Lower vehicle from jack stands and remove safety equipment
5. Reconnect 12V battery if disconnected for any reason during final steps

Verification

• Start vehicle and verify no warning lights or coolant temperature fault codes appear on the instrument cluster
• Using diagnostic scanner, monitor live coolant temperature data to confirm sensor is reading within expected range (typically 60-90°F at cold start)
• Allow vehicle to remain in READY mode for 5-10 minutes while monitoring coolant temperature to verify reading increases gradually and appropriately
• Inspect under vehicle for any coolant leaks around the sensor installation point; look for drips or wet spots
• Verify coolant level in reservoir has not dropped after operation; top off if necessary
• Test drive vehicle for 10-15 minutes and monitor for any temperature warnings or performance issues
• After test drive, recheck coolant level when system has cooled and top off if needed to account for air purging during operation
• Perform final diagnostic scan to confirm no new fault codes have been generated

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