So Fix it

Park your Lexus SC400. Set the parking brake, and open the engine hood. Let the engine cool completely before proceeding.

Locate the O2 sensor. Its in the lower engine area on the passenger side, threaded into the exhaust manifold.

Remove the wire from the sensor. Spray some anti-seize spray at the bottom of the sensor where it goes into the manifold. Let the fluid penetrate for a few minutes before proceeding.

Remove the sensor with the appropriate size socket and ratchet. Rotate the sensor counter-clockwise to loosen.

Install the new sensor into the hole and tighten firmly. Attach the wire and the job is finished.

Put the key into the ignition and turn it to the "On" position.

Connect the Lexus diagnostic tester to the DLC3 port on the vehicle. The DLC3 port is located on the lower left side panel and is clearly labeled.

Turn on the diagnostic tester and select the "Customize" option.

Select "Verify Connections," press the "Yes" button, and press "Enter."

Select function "08" which is "Light Control."

Go to "Light Off Delay" and set it to your desired value. You can either choose 30 seconds, 60 seconds, 90 seconds or immediate off.

Apply the parking brake and set wheel chocks behind the rear wheels. Raise and support the front of the Lexus using a floor jack and jack stands positioned under the front sub-frame. Lower the car onto the stands slowly so that the weight of the car is supported evenly by the jack stands. Remove the floor jack.

Allow the exhaust system to cool completely. The catalytic converters on the LS400 operate at a high temperature (over 600 degrees Fahrenheit) and can cause severe burns if not allowed to cool sufficiently prior to working on the system.

Spray the attaching bolts on the converter with a liberal coating of penetrating oil and allow it to sit for a few minutes. Remove the two rear mounting bolts that attach each of the converters to the exhaust system using a 13mm socket and ratchet to turn the bolt while holding the 15mm nut with a wrench. Pry the exhaust system back away from the converter and pull the exhaust downward.

Remove the three 13mm nuts that attach the converter to the exhaust manifold and pull the converter off the manifold studs. Use a new exhaust gasket between the converter and manifold. Bolt in the new converter, leaving the nuts loose so the converter can be moved slightly while lining up the rest of the exhaust system.

Raise the exhaust system and pry it back until it can be slipped onto the converter. Place a new gasket between the converters and the exhaust system. Install and tighten all of the nuts and bolts securely.

Locate the ID tag of your Lexus. This is on the drivers side door jamb and the label at the top of the tag will read "MFD. BY: TOYOTA MOTOR CORPORATION." The tag will either be white or black and easily identifiable, as it is the most prominent piece on the door jamb.

Identify the trim code on the tag. On the lower left-hand corner of the tag, you will see written "C/TR:." Following this will be one three-number-and-digit sequence and one four-digit-and-number sequence, separated by a dash. The second sequence is the paint code for the trim on your Lexus. For example, if you see 8J5/LA20, the exterior code is 8J5 and the trim code is LA20.

Mark down the trim code. If you need touch-ups or re-painting, you will need to match this code with the paint at the manufacturer or car dealership to ensure that the new paint matches the original.

Access the Toyota Reference database online for more specific information on your trim code and paint colors. Lexus changes the codes every year and on this site you will find more detailed information on what these codes are and to which colors they correspond.