Replacing the taillight bulbs in your Lexus GS300 requires the removal of the taillight assembly from the car. The GS300 left the factory with one of two possible taillights: a standard taillight assembly using a 2825 bulb and the other, an LED taillight assembly. The owner's manual states that the LED taillights, if you have them, must be serviced at a dealership. If you have the standard bulbs, you can change them in just a few minutes in the driveway with basic hand tools.
Open the trunk of your GS and locate the trim panel that covers the inside of the trunk directly behind the taillight assembly. There are two large plastic wing nuts on the panel; remove them. Set them aside along with the trim panel for now.
Locate the four 10 mm retaining nuts that hold the taillight assembly to the car. Remove the nuts with a 10 mm deep socket and a ratchet. Slide the taillight assembly out far enough to access the bulb sockets on its back side.
Turn the socket counterclockwise, unlocking it from the assembly, then remove the socket and the bulb. Pull the bulb out of the socket and discard it. Push a new 2825 bulb into the socket, making sure it fully seats in the socket.
Insert the bulb and socket into the rear of the taillight assembly and turn it clockwise, locking it in place. Slide the assembly into place on the car and install the four retaining nuts on the studs inside the trunk of the car. Tighten them with a 10 mm deep socket and ratchet until they are snug.
Position the trim panel back on the rear wall of the trunk; cover the retaining studs and nuts. Thread the two plastic wing nuts on far enough to hold the trim panel on securely but do not over-tighten them or you will crack the panel. Close the trunk or move to the other side and repeat the process.
