How Do I Run Wires Through the Firewall on a 2002 GMC Sierra?
- 1). Pop the hood. Locate the large circular grommet on the driver's side of the firewall, located underneath the brake booster.
- 2). Cut an X-shaped slit in the grommet using the straight razor blade, making the x slightly larger than the wire you need to run through the firewall.
- 3). Push the wire through the slit in the grommet with your hands. If the wire can't fit in the slit, then cut the slit slightly larger with the razor blade.
- 4). Move to the underside of the dash and shine the flashlight up the firewall to locate the wire that you pushed through the grommet in step 3. Pull the wire through the firewall as needed with your hands.
