Turn off your 1994 Lexus 400 engine. Open the hood.
Unscrew the top screw at the junction of the headlight assembly and the corner fender. Pull the fender away slightly from the headlight when the screw is removed.
Pull the parking light assembly out of the cavity by disconnecting the parking light wiring harness and setting it aside.
Remove the four 10 mm bolts around the perimeter of the headlight assembly using your socket wrench.
Hold onto the headlight assembly and swivel it away from the engine compartment toward the opened corner fender. Do not jerk it completely away from the car, because its wiring harness is still connected.
Pull the wiring harness off the rear of the headlight. Twist the black ring counterclockwise to remove it from the headlight. Pull the bulb straight out of the housing assembly. Insert a new bulb directly into the socket. Remount the black cover ring by twisting it on clockwise. Plug back in the wiring harness. Reinsert the headlight assembly and mount the four bolts. Slide in the parking light assembly and attach it to its wiring harness.Unlike many vehicles, the 1994 Lexus 400 requires you to remove the headlight assembly to replace a headlight bulb that has burned out. Four bolts must be removed to take out the assembly, and if the bolts are at all worn or rusted, a lot of force may be needed to remove them. The bolts are easy to see and are easily accessible, however.