The Lexus S430 is actually classified as an SC430. The "C" stands for "coupe," which is the only way the S430 model is available. The 430 is related to the 4.3-litre V-8 engine. First manufactured in 2001, the SC430 features four oxygen sensors. Two located up front on the converters bolted to the manifolds (one per engine side), and two more located near the two rear catalytic converters. Although the procedure to replace any of them is the same, the sensors are different forward and aft, and defining which sensor has failed will require a code reader/scan tool and knowing where your number one cylinder is located.
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Things you need
- Lexus SC430 repair manual
- Code reader/scan tool
- Oxygen sensor socket and a flex-head ratchet
- Replacement oxygen sensor (direct-fit only)
- Car lift (optional)
Determine which oxygen sensor needs to be replaced. Plug a code reader or scan tool into the diagnostic link connector located beneath the driver's side dashboard. Turn the Lexus SC430 ignition to the "accessories" position. Follow the directions of the code reader or scan tool to discover which sensor has failed. Bank one-sensor one is the forward-most (towards the engine) sensor located on the same side as the number one cylinder. Bank one-sensor two is downstream on the same side, near the rear catalytic converter. Respectively, the two sensors for bank two are positioned in the same way on the opposite side of the engine and exhaust.
Lift the SC430 if you're replacing one of the number two sensors. The number one sensors may be easier to access from the engine compartment on either side of the engine by the manifold.
Follow the wire harness of the sensor you're going to replace until you find the plug. It will be eight or nine inches away from the sensor. Disconnect the plug of the sensor from the plug of the wire harness.
Use the oxygen sensor socket and a flex-head ratchet to remove the sensor from the exhaust porthole. A 22mm wrench can also be used, but the amount of room available may restrict its effectiveness. Turn the sensor counterclockwise from the exhaust porthole to remove. Remove the sensor.
Thread the new direct-fit sensor into the exhaust porthole by hand to assure you're not cross-threading it. Snugly tighten the sensor with the socket and ratchet (or the 22mm wrench). Do not over-tighten the sensor because the threads on the sensor can easily strip.
Plug the sensor wire plug back into the wire harness plug.
Rescan the PCM using the code reader or scan tool. Follow the directions to erase the code to clear the check engine light.
Tips and warnings
- Using a direct-fit (aftermarket or original equipment) oxygen sensor will assure quality and name-brand of the sensor, and will also be easier to install than a universal sensor. Universal sensors often require cutting and splicing wires instead of simply unplugging. The problem there is that the colours of the universal sensor rarely match up to the wires of the harness, thereby confounding the project.
- Safety glasses should be worn any time you're beneath a vehicle to prevent rust or other debris from contaminating your eyes.