The headlight relay in a 2015 GMC Sierra is located in the underhood fuse box. This fuse box contains non-serviceable Printed Circuit Board (PCB) relays that are internal to the block. The high beam control relay is specifically housed within this underhood fuse box.

Underhood Fuse Box

The underhood fuse box, also known as the engine compartment fuse block, is the primary location for the headlight relay in your 2015 GMC Sierra. This fuse box contains various electrical components, including fuses and relays that control different vehicle systems.

Accessing the Underhood Fuse Box

To access the underhood fuse box:

  • Open the hood of your GMC Sierra
  • Locate the fuse box near the driver's side of the engine compartment
  • Remove the fuse box cover to reveal the internal components

Headlight Relay Specifics

The headlight relay in your 2015 GMC Sierra is designed as an internal component of the fuse block. This means:

  • The relay is not a separate, replaceable unit
  • It's integrated into the PCB of the fuse block
  • Troubleshooting may require professional diagnostic tools

High Beam Control

The high beam control relay, which is part of the headlight system, is also located within this underhood fuse box. This relay controls the switching between low and high beam headlights.

Troubleshooting Headlight Issues

If you're experiencing headlight problems:

  • Check the relevant fuses in the underhood fuse box first
  • Inspect the wiring harness for any visible damage
  • If the issue persists, it may be related to the internal relay or control module

Important: Due to the integrated nature of these relays, replacement or repair often involves replacing the entire fuse block assembly. It's recommended to consult with a certified GMC technician for accurate diagnosis and repair.

Remember, while you can't directly access or replace the headlight relay, understanding its location can help in diagnosing headlight-related issues in your 2015 GMC Sierra.