Replacing The Air-Fuel Ratio Sensor In Your Lexus Rx300

The air-fuel ratio sensor in your Lexus RX300 is an important component that helps to optimise the performance of the catalytic converter and keep emissions low. If the check engine light is on and your car is throwing codes such as P0171, P1130, or P1150, you may need to replace the air-fuel sensor. This is a DIY task that you can do yourself, but you will need to purchase a replacement part. The Lexus part number for the RX300 air-fuel sensor is 89467-48011, and the OEM part made by Denso is 234-9009. These parts are available from a variety of retailers, including Lexus, Toyota, eBay, and Amazon, with prices ranging from $126 to $300. Once you have the part, the process of replacing the sensor involves putting the car on ramps, unplugging and unscrewing the old sensor, and then inserting and plugging in the new sensor. Finally, you will need to reset the check engine light.

Testing the sensor

Testing the air-fuel ratio sensor on a Lexus RX300 can be done by checking the sensor signal with a scan tool. The first step is to check for related technical service bulletins (TSBs) and inspect the wiring and connector of the sensor for any damage, corrosion, or loose pins. Then, depending on the trouble code, the sensor signal must be tested with a scan tool.

For example, when the engine is revved, the signal may jump to "rich", and as the RPM drops and the fuel is cut off, the sensor may indicate "lean". After that, the signal should return to normal, indicating that the air fuel sensor is functioning properly. It is important to note that the sensor may work properly at the time of inspection, in which case your mechanic may recommend replacing the sensor to eliminate the possibility of an intermittent fault.

Additionally, it is worth mentioning that the front air/fuel sensor is easier to test compared to the rear sensor due to its location.

Shopping for a replacement part

When shopping for a replacement air/fuel sensor for your Lexus RX300, it's important to get a part that is compatible with your car's make and model. The Lexus part number for the RX300 air/fuel sensor is 89467-48011, and the OEM a/f sensor is made by Denso, with the part number 234-9009. These two are equivalent.

You can purchase the part from Lexus for around $300, or from Toyota for about $200. Online retailers such as eBay and Amazon also offer more affordable options, with prices ranging from $126 to $150. When buying online, be sure to check the seller's reviews and ratings to ensure you're getting a quality product.

Some trusted brands for air/fuel sensors include DENSO and NTK, which you can find at Advance Auto Parts. Their products are manufactured and tested to meet strict OE standards, ensuring a precise replacement and a perfect first-time fit.

When shopping for a replacement sensor, it's important to consider the length of the sensor, as well as the number of wires it has. Sensors typically range from 7 to 20 inches in length and have 4 wires. Additionally, features such as high-temperature signal output, air tightness, continuity, and heat resistance are crucial for optimal efficiency and performance.

Before purchasing, be sure to verify that the part is compatible with your Lexus RX300 by checking the compatible vehicle list provided by the seller or retailer.

Overview of the replacement process

The air/fuel sensor in a Lexus RX300 (1999-2003) is located on the rear three cylinders exhaust manifold (back sensor) or the front (front sensor). The Lexus part number for the RX300 air/fuel sensor is 89467-48011. The OEM a/f sensor is made by Denso and the Denso part number is 234-9009.

The process of replacing the air/fuel sensor in a Lexus RX300 involves the following steps:

• Put the car on ramps and spray the sensor with WD-40 or PB Blaster. Allow the car to cool off before beginning work, as running the car even for a few seconds will heat up the exhaust manifold.
• Unplug the old sensor wire. This can be done from the top through the engine compartment by pressing the tab and pulling the plug out.
• Remove the old sensor using a 7/8" wrench with an elbow, a sensor socket with a breaker bar, or a straight 22mm wrench.
• Apply anti-seize compound to the threads of the new sensor, avoiding the sensor itself.
• Insert the new sensor and tighten it snugly.
• Plug in the new sensor wire.
• Reset the check engine light (CEL) by pulling the ECU fuse from the engine compartment for about 10 minutes.

Putting the car on ramps

To replace the air-fuel ratio sensor in your Lexus RX300, you'll first need to put your car on ramps. Here's a detailed, step-by-step guide on how to do that:

Choosing the Right Car Ramps

First, you need to select a suitable pair of car ramps. Consider the following factors:

• Maximum Rated Load: Choose ramps with a maximum rated load well above your car's Gross Vehicle Weight (GVW). This information can be found on your driver's door sticker or in the owner's manual.
• Country of Manufacture: Ramps made in the US and the European Union are typically subject to stricter quality control standards.
• Read Reviews: Do your research and read reviews from other users to gauge their experiences and identify any potential issues.
• Low-Clearance Ramps: If you have a sports car or a vehicle with low ground clearance, consider investing in low-clearance ramps, which have a more gradual incline to prevent undercarriage scraping.
• Rubber Stops: Look for ramps with rubber stops or components on the underside to prevent sliding when the car drives up.
• Damage: Inspect the ramps for any signs of damage, such as rust or cracks, and refrain from using damaged ramps.
• Wheel Chocks: Purchase wheel chocks to use in conjunction with the ramps for added safety. Soft rubber chocks are ideal for smooth or slippery garage floors.

Positioning the Car and Ramps

Once you've selected the appropriate ramps, it's time to position your car and the ramps:

• Slide the ramps against the front tires, centering the lower slope of each ramp with one tire. Ensure the ramps are straight by sighting along the side of the car.
• If your wheels are turned, adjust them so they point straight ahead.
• Always work on a hard, level, paved, or concrete surface. Avoid wet or slippery surfaces, as they can make it challenging to drive up the ramps without sliding.

Driving Up the Ramps

Now it's time to drive your Lexus RX300 up the ramps:

• Get into your car and drive forward directly up the center of the ramps.
• Once you've driven up, get out and confirm that the front wheels are centered and fully on the flat portion of the ramps. If not, drive back down and reposition.
• Engage the parking brake to ensure the car doesn't roll back down the ramps.
• Rock the car gently to make sure it's stable.
• Place two wheel chocks around one of the back wheels—one in front and one behind—for added safety.

Now that your Lexus RX300 is securely positioned on the ramps, you can proceed with replacing the air-fuel ratio sensor. Remember to exercise caution and follow safety protocols throughout the process.

Unplugging the sensor

Once the socket is located and the tab is pressed, the wire should be easy to unplug. Be sure to do this carefully, as you do not want to cause any damage to the surrounding components. It is also important to ensure that the engine is cool before beginning this process, as the exhaust manifold can become very hot.

In addition, it is recommended to spray the sensor with WD-40 or PB Blaster the night before to make it easier to work with. This will help to loosen any built-up residue and make the unplugging process smoother.

By following these steps, you will be able to successfully unplug the air-fuel ratio sensor in your Lexus RX300, setting you up for the next steps in the replacement process.

Frequently asked questions