Main Relay

This procedure covers the replacement of the main power distribution relay in the engine compartment fuse box, which controls power to various vehicle systems.

Warnings

Tools required

Parts

• Main power relay × 1 — Use OEM specification

Preparation

1. Park vehicle on level surface and engage parking brake
2. Turn ignition to OFF position and remove key
3. Allow engine to cool if recently operated
4. Open hood and secure with prop rod

Procedure

1. 1

   Disconnect battery negative terminal
   Locate the battery in the engine compartment. Using a 10mm socket, loosen the negative (-) battery terminal bolt. Remove the cable from the terminal and secure it away from the battery post to prevent accidental contact.
   Torque spec

   Battery Terminal Bolts6 Nm (4 lb-ft)
2. 2

   Wait for system discharge
   Wait at least 2 minutes after battery disconnection to allow capacitors in the electrical system to discharge completely. This ensures all residual power is drained from control modules.
3. 3

   Locate engine compartment fuse box
   The main fuse box is located on the driver's side of the engine compartment, near the firewall. Identify the black plastic housing with the fuse box cover.
4. 4

   Remove fuse box cover
   Release the clips securing the fuse box cover by pressing the tabs on each side and lifting upward. The cover will reveal the fuse and relay layout diagram on its underside. Set the cover aside in a clean area.
   Torque spec

   Cover Screws12 Nm (9 lb-ft)
5. 5

   Identify main relay location
   Using the diagram on the fuse box cover, locate the main power relay. It is typically a larger relay in the center or upper section of the fuse box. The relay will be labeled on the diagram - common designations include 'MAIN PWR' or similar marking.
6. 6

   Remove the main relay
   Grasp the relay firmly and pull straight upward with steady pressure. If the relay is difficult to remove, use a relay puller tool or carefully work a flathead screwdriver under opposite edges, alternating sides to work it free. Avoid rocking the relay side-to-side excessively to prevent damage to the socket terminals.
7. 7

   Inspect relay socket
   Examine the relay socket for any signs of corrosion, discoloration, or damage to the terminal contacts. If corrosion is present, clean the contacts with a wire brush or electrical contact cleaner. Ensure all terminals are straight and making proper contact. If socket damage is found, the entire fuse box may require replacement.
8. 8

   Install new main relay
   If desired, apply a small amount of dielectric grease to the relay terminals to prevent future corrosion. Align the new relay with the socket, ensuring the orientation matches the original (relays are keyed and will only fit one way). Push the relay firmly into the socket until it is fully seated and flush with surrounding relays.
9. 9

   Reinstall fuse box cover
   Position the fuse box cover over the fuse box, aligning the mounting tabs. Press down firmly until all clips engage and the cover is secure. If the cover has retaining screws, tighten them to specification.
   Torque spec

   Cover Screws12 Nm (9 lb-ft)
10. 10

    Reconnect battery negative terminal
    Place the negative battery cable back onto the negative battery post. Ensure the connection is clean and secure. Tighten the battery terminal bolt to the specified torque. Do not overtighten as this can damage the battery post or terminal.
    Torque spec

    Battery Terminal Bolts6 Nm (4 lb-ft)

Reassembly

1. Ensure all fuse box cover clips are fully engaged
2. Verify battery terminal connection is tight and corrosion-free
3. Double-check that no tools or parts were left in the engine compartment

Verification

• Turn ignition to ON position (do not start engine) and verify dash lights illuminate normally
• Start the engine and confirm it starts without hesitation
• Check that all electrical accessories function properly (windows, radio, lights, climate control)
• Verify no warning lights remain illuminated on the instrument cluster
• Test power windows by cycling them down and up, then auto-up to re-initialize if needed
• If any warning lights persist, use a diagnostic scanner to check for stored fault codes

Related trouble codes on this vehicle

Codes that commonly send this job to the bay — tap one for symptoms, causes, and diagnostic steps.

Chasing one of these codes and not sure which part is guilty? Ask a master mechanic about YOUR car →

More procedures for this vehicle