Replacing Air-Fuel Ratio Sensor In Toyota 4Runner: Step-By-Step Guide

If you're looking to replace the air fuel ratio sensor in your Toyota 4Runner, you've come to the right place. This is a step-by-step guide on how to do it. First, a little background: the air fuel ratio sensor is a type of oxygen sensor that helps your vehicle burn fuel efficiently and cleanly. Now, to replace it, follow these steps:

1. Check if your vehicle is a California emissions vehicle. This is important because the part number will differ. Look for a label on the underside of the hood or check if you have two small catalytic converters.

2. Find the part number: Every parts store or online catalog will determine the part number based on the year, engine size, transmission type, and California emissions status.

3. Shop around for the best price on the part.

4. Locate the sensor: it is attached to the exhaust pipe just before the catalytic converter.

5. Prepare the necessary tools: you will need a 10mm socket or wrench to remove the clamp holding the connector, and a 12mm wrench to remove the nuts holding the sensor.

6. Apply penetrating oil to the nuts holding the sensor and allow it to soak.

7. Raise your vehicle: use a hydraulic floor jack to lift your truck and place it on jack stands for safety.

8. Remove and replace the sensor: disconnect the wiring harness, remove the old sensor, and install the new one with a gasket for a tight seal.

9. Clear the CEL (Check Engine Light): you can use a code scanner or disconnect the negative battery cable for at least one minute.

There you have it! You've successfully replaced the air fuel ratio sensor in your Toyota 4Runner.

Finding the correct part number

The first step in finding the correct part number for your air fuel ratio sensor is determining whether your Toyota 4Runner is a California emissions vehicle. This is important because the part number will differ depending on whether your vehicle is a California emissions vehicle or not. You can identify this in two ways:

• Check the underside of the hood, where the engine type is provided. A label indicating California emissions will be present if your vehicle is a California emissions vehicle.
• Look at the catalytic converters. If your car has two small catalytic converters, it is a California emissions vehicle. If it has one larger catalytic converter, it is not.

Once you have determined whether your vehicle is a California emissions vehicle, you can proceed to find the part number. Parts stores or online catalogs like Denso and Bosch will determine the part number based on the following factors:

• Year of your vehicle
• Engine size
• Transmission type
• Whether it is a California emissions vehicle or not

For example, if you own a 1999 Toyota 4Runner with a 6-cylinder engine, automatic transmission, and it is a California emissions vehicle, the Denso part number is 234-9002, and the Bosch part number is 13613 or F00E260829.

It is important to note that the part number may vary depending on the specific year, model, and configuration of your Toyota 4Runner. Therefore, it is always a good idea to consult a reliable parts catalog or a mechanic to ensure you get the correct part number for your vehicle.

Additionally, when purchasing parts, it is recommended to shop around as prices can vary significantly between different stores and suppliers.

Shopping around for the best price

When shopping around for the best price on a new air fuel ratio sensor for your Toyota 4Runner, it's important to consider both the cost of the part itself and the cost of any labour required for installation.

First, you'll need to determine the correct part number for your vehicle. This will depend on the year, engine size, transmission type, and whether your vehicle is a California emissions vehicle. You can refer to your owner's manual or consult with a trusted mechanic to determine the correct part number.

Once you have the part number, you can start comparing prices from different retailers and suppliers. It's worth checking with both online stores and local shops in your area. Don't forget to factor in shipping costs if you're ordering online.

• Advance Auto Parts offers sensors starting from $63.68, with prices varying by brand and specifications.
• PartsGeek.com offers OEM, stock replacement, or aftermarket parts at competitive prices. They suggest that buying the sensor yourself may be cheaper than purchasing it from a dealer or mechanic.
• Auto parts stores like Autozone, O'Reilly, and Napa offer a range of prices, with one user reporting prices from $120 to $360 for the same part number and manufacturer.

It's worth noting that California emissions sensors tend to be more expensive, so if your vehicle doesn't fall into this category, you may be able to find a more affordable option.

When making your purchase decision, be sure to consider not only the price but also the quality and reliability of the part. Look for trusted brands and consider reading reviews from other customers to get a sense of their experience with the product.

Additionally, if you plan to install the sensor yourself, factor in the cost of any necessary tools and equipment, as well as your time and effort. If you're not comfortable with the DIY approach, you'll need to include labour costs from a mechanic or specialist in your overall budget for the repair.

Locating the sensor

To get a better view of the sensor, you will need to go under the truck. Use the passenger side door to crawl underneath. Locate the exhaust pipe and look for the catalytic converter in between the front and rear sections of the pipe. The rear sensor, denoted as bank 1, sensor 2, will be just behind the converter, closer to the rear end. The forward sensor, or bank 1 sensor 1, will be mounted above the transmission case, in front of the catalytic converter.

The forward sensor can be a bit tricky to reach, especially for individuals with bigger arms. However, with a bit of patience and some basic tools, you can certainly access it and replace it yourself.

Preparing the necessary tools

Before beginning the process of replacing the air fuel ratio sensor, it is important to have all the necessary tools and materials on hand to ensure the job is done efficiently.

First, park your Toyota 4Runner on a flat, hard surface and ensure that the transmission is in park for automatics or in first gear for manuals. This step is only necessary for vehicles with all-wheel drive or rear-wheel-drive transmissions. Place wheel chocks around the rear tires and engage the parking brake to prevent the vehicle from moving.

Next, you will need to raise the vehicle. Use a floor jack to lift the vehicle at its specified jacking points until the wheels are completely off the ground. Once the vehicle is raised, place jack stands under the jacking locations and lower it onto the stands. For modern cars, the jacking points are usually on the pinch weld just under the doors along the bottom of the car. However, it is best to refer to the vehicle's owner's manual for the proper jacking locations.

Now that the vehicle is securely raised and supported, you can crawl under it to locate the air fuel ratio sensor. The sensor is attached to the exhaust pipe, just before the catalytic converter. If your vehicle has two catalytic converters, the sensor will be before the first one.

To remove the sensor, you will need the following tools:

• A ratchet with metric and standard sockets
• An offset 12mm wrench or ratchet and 12mm socket
• A small flat-head screwdriver
• A steel wire brush and lubricant (optional)
• A new gasket for the mounting flange
• Anti-seize compound

If the sensor is difficult to remove due to rust or other factors, you may also need:

• A small portable torch
• A breaker bar
• An air fuel ratio sensor socket

Removing and replacing the sensor

The air-fuel ratio sensor is located on the exhaust pipe, just before the catalytic converter. To replace the sensor, first locate the sensor by looking for the exhaust pipe under the passenger side door. The sensor will be attached to the exhaust pipe just before the catalytic converter.

Before starting work, ensure the exhaust pipe is cold. Then, spray the two 12mm nuts holding the sensor in place with penetrating oil to loosen them. Allow the oil to sit for at least 15-20 minutes, but preferably overnight.

Next, use a 10mm socket or wrench to remove the clamp holding the connector in place, and a 12mm wrench to remove the two nuts holding the sensor in place. You may need to use a small flat screwdriver to pry the connector open. Once the connector is open, remove the sensor and the gasket.

Now it's time to install the new sensor. Place the new gasket in position, then screw the new sensor into the flange. Tighten the 12mm nuts to secure the sensor in place. Reconnect the wiring harness by inserting the male connector (sensor side) into the female connector (vehicle side) and secure it with the 10mm bolt.

Finally, clear the CEL (check engine light) by using a code scanner or disconnecting the negative battery cable for at least one minute.

Tips and Tricks

• Shop around for the best price on the sensor part. Prices can vary significantly between shops and online retailers.
• If you have large arms or hands, consider accessing the front sensor from inside the cabin to make it easier to disconnect the wiring harness.
• Use a hydraulic floor jack to lift your truck and place it on jack stands before starting work.
• Use a steel wire brush and lubricant to clean the nuts before installing the new sensor.
• Be careful not to touch the sensor bulb during the removal or installation process.
• Use anti-seize compound on the bolts when installing the new sensor.
• Double-check that your new sensor matches the old one before installing.

Frequently asked questions