The radio antenna on a Toyota Matrix is mounted on the roof at the rear end of the vehicle. The antenna wire runs from the antenna through the headliner, down the windshield pillar on the passenger's side and to the radio unit. It is possible to remove and replace the antenna itself without messing with too much of the wire. You can do this if you need to replace a damaged antenna or upgrade to a stronger one.
Unscrew the antenna mast, and remove it from the base.
Grasp and pry off the trim panel inside the car bordering the headliner on the rear passenger's side. You might need the help of a trim stick. This will uncover the headliner fasteners at this end.
Remove the fasteners for the headliner using a screwdriver, and look for the headliner to drop low enough for you to access the antenna base's fastener.
Unscrew and remove the nut for the antenna base with a wrench. Disconnect the antenna from the rest of the wire, and remove the base from the roof.
Install the new antenna base into the mounting hole within the roof -- you might need another person to do this from outside the vehicle -- and secure it with its nut. Connect the mast to the vehicle's antenna wire.
Fasten the headliner back into place, and re-install the trim along the upper edge.
Thread and screw the mast for the new antenna onto the base.
