Horn Relay

This procedure covers the replacement of the horn relay in a 2025 Rivian EDV 500 commercial electric van, which is typically located in the front power distribution module.

Warnings

Tools required

Parts

• Horn relay × 1 — Use OEM specification
• Panel clips (if damaged) × 5 — Rivian service parts

Preparation

1. Park vehicle on level surface and engage parking brake
2. Power down vehicle completely and remove key fob from cabin
3. Allow vehicle to sit for 2 minutes to allow systems to enter sleep mode
4. Open front hood and secure in raised position
5. Photograph existing wiring and relay configuration for reference

Procedure

1. 1

   Disconnect 12V battery
   Locate the 12V battery in the front compartment. Using a 10mm socket, loosen and remove the negative terminal clamp first, then the positive terminal. Secure cables away from battery posts using a tie or tape to prevent accidental reconnection.
2. 2

   Remove front underhood cover panels
   Using the Torx T20 driver, remove the fasteners securing the plastic underhood cover panels. Carefully use panel removal tools to release any push-pin clips. Set panels and hardware aside in organized manner for reinstallation.
3. 3

   Locate power distribution module
   Identify the front power distribution module (PDM) located on the driver side of the front compartment. The module is a black box with multiple relay positions and fuse locations. Clean any dirt or debris from the exterior of the module.
4. 4

   Access relay compartment
   Release the retaining clips on the power distribution module cover by pressing the tab releases on both sides. Lift the cover straight up and remove. The relay diagram should be printed on the underside of the cover or on the module itself.
5. 5

   Identify horn relay position
   Using the relay diagram, locate the horn relay position. The horn relay is typically labeled as 'HORN' or with a horn symbol. Note the relay orientation by observing the alignment tab position. Take a reference photo if diagram is unclear.
6. 6

   Test existing relay (if diagnostic needed)
   If diagnosing horn failure, use the digital multimeter to test relay operation. Set multimeter to continuity mode and check for proper switching action. Document results. If relay is confirmed faulty, proceed with removal.
7. 7

   Remove failed horn relay
   Grasp the horn relay firmly and pull straight up with steady pressure to disengage it from the socket. The relay should release with moderate force. If stuck, gently rock side-to-side while pulling upward. Inspect socket terminals for corrosion or damage.
8. 8

   Inspect relay socket and terminals
   Examine the relay socket terminals for any signs of burning, corrosion, or damage. Check for bent pins or debris in the socket. If corrosion is present, clean terminals with electrical contact cleaner and allow to dry completely before installing new relay.
9. 9

   Install new horn relay
   Align the new horn relay with the socket, ensuring the orientation tab matches the socket key. Press the relay firmly straight down into the socket until it fully seats with an audible click. The relay should sit flush with surrounding relays.
10. 10

    Reinstall power distribution module cover
    Position the PDM cover over the module, aligning it with the housing. Press down on all edges until the retaining clips engage with audible clicks. Ensure cover is fully seated and secure.
11. 11

    Reinstall underhood panels
    Replace all underhood cover panels in reverse order of removal. Install push-pin clips first, then secure with Torx fasteners. Ensure all panels are properly aligned and seated before tightening fasteners.
12. 12

    Reconnect 12V battery
    Reconnect the positive terminal first, tightening the 10mm clamp bolt securely. Then connect the negative terminal and tighten. Ensure both connections are clean and tight to prevent voltage drops.

Reassembly

1. Verify all underhood panels are properly secured and aligned
2. Ensure no tools or parts remain in the front compartment
3. Confirm battery terminals are tight and corrosion-free
4. Check that power distribution module cover is fully latched

Verification

• Close hood and enter vehicle
• Power on the vehicle and wait for all systems to initialize
• Press the horn button on steering wheel and verify horn operates correctly
• Test horn multiple times with short and long presses to confirm reliable operation
• Check for any warning lights or error messages on instrument cluster
• Use vehicle diagnostics (if available) to verify no horn-related fault codes are present
• Verify horn operates at proper volume without buzzing or weak sound

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