How often to replace o2 sensors. 1 or 2 wire Oxygen sensors - have a typical service life of 50,000 Km’s 3 or 4 wire Oxygen Sensors (Thimble type) - have a typical service life of 80,000 Km’s Planar Type (Thick film) Oxygen sensors- have a typical service life of 150,000 Km’s O2Sensors.com.au recommends Oxygen Sensor replacement every 80,000.
Chris Gash
I've got a 1998 Ford Taurus, and the Check Engine light came on. Checking the code with an OBD-II scanner revealed a bad oxygen sensor. What's the best way to replace it?
Your car's computer uses data from the O2 sensors to determine the effectiveness of the catalytic converter and how much fuel to inject. So they're critical pieces. Luckily, replacing one is relatively straightforward. Unfortunately, original-equipment oxygen sensors, offered by the manufacturer, can be pricey. The solution is to buy a cheaper, universal-replacement sensor from your local auto parts store.Ah, but all sensors are not the same. Older cars typically used basic units with just one wire (the wire carried the signal, while the unit simply grounded to the exhaust pipe). Newer cars are fitted with heated O2 sensors with up to four wires, allowing the sensor to reach its base 250 F operating temperature more quickly. The most surefire way to buy the right replacement is to first remove the bad one and take it with you to the store.
The sensor is typically almost welded to the exhaust, so apply a liberal spray of penetrating oil to the threads of the sensor and let it loosen the joint. Unplug the sensor from the wiring harness, and get a special O2 sensor socket from the auto parts store (some loan them out for free) and remove the old sensor from the exhaust bung. If the sensor won't budge, try more penetrating oil or attempt the removal with the engine warm (be careful not to burn yourself).
The universal replacement may come with an adapter plug to mate the new sensor to the car's wiring harness. If so, use the adapter. Never cut the wires on O2 sensors that come with adapters, because, interestingly, these types of sensors 'breathe' through the wires. Every O2 sensor works by comparing exhaust gas to outside air—the difference in oxygen levels creates a voltage that's read by the car's computer. As a result, cutting the wires and soldering them clogs that minute pathway and renders the sensor useless.
There are, however, some sensors that sample outside air near the unit's base and therefore come with just bare wires. If you obtain one of these, you'll need to cut the plug off the old sensor and splice it to the new one. Strip the insulation off the ends, slide sections of heat-shrink tubing over the sensor wires, and splice the joint together with solder. Finish by applying heat, sealing the joint.
Your new O2 sensor should be handled like a piece of china. Do not allow the tip to touch anything—it may become contaminated. Apply a small amount of anti-seize to the threads and hand-tighten the sensor in the exhaust bung, being careful to keep the tip away from the sides. Use the sensor socket to tighten the O2 sensor to three-quarters turn past finger-tight, depending on the manufacturer's recommendation. Finally, reroute the wire and attach the connector. Be sure to keep the wire from direct contact with high-heat sources.
The oxygen sensor in your vehicle measures oxygen levels in the exhaust gases exiting the engine. This information is used by the Powertrain Control Module (PCM) to determine the correct air to fuel ratio for your engine in real time. The sensor is located in the exhaust system and allows the fuel injection and engine timing to work efficiently, which assists with emissions control. The oxygen sensor transmits the data to the vehicle’s PCM to maintain the optimal air to fuel ratio for your engine. A bad or failing oxygen sensor will have a negative impact on environmental emissions and engine performance, so there are a 3 things to watch out for before your oxygen sensor completely fails.
1. Check Engine Light comes on
The first line of defense is the Check Engine Light. The Check Engine Light will illuminate if you have a bad or failing oxygen sensor. As soon as this light comes on, contact a professional automotive technician for a Check Engine Light inspection. This light can come on for many different reasons, so it is important to have it looked at by a professional who can correctly diagnose the exact cause. If you have high a mileage vehicle, there's a good chance it has a bad oxygen sensor in need of replacement.
2. Bad gas mileage and rotten egg smell
If the oxygen sensor is going bad, the fuel-delivery and fuel-combustion systems will be thrown off. If a bad oxygen sensor disrupts the air to fuel ratio mixture, or too much fuel is injected into the engine, your vehicle's gas mileage will be reduced. This excess fuel in the engine can produce a sulfuric, rotten egg smell, and may even produce black smoke from the exhaust. If yourself filling up your gas tank more often, keep a record of how many gallons you fill up with and how often. If it is more than normal, have a professional mechanic check out your oxygen sensor.
3. Rough engine idle and misfires
As your oxygen sensor is going bad you may notice your vehicle is running rough, misfiring or running irregularly while idling. You may also observe other engine performance problems, such as loss of power, hesitation, or stalling. Since the oxygen sensor output helps control engine timing, combustion intervals, and the air to fuel ratio, a bad sensor can disrupt these engine functions, causing a rough or irregular engine idle and other engine-related issues.
When to replace the sensor
If your vehicle was manufactured within the past 15 years, the oxygen sensor should be replaced every 60,000 to 90,000 miles. This sensor does wear out and will need replacement over time. Replacement of a bad or failing oxygen sensor will reduce the level of emissions your vehicle puts into the atmosphere while keeping your engine running smoothly and properly. As soon as you notice your Check Engine Light, poor gas mileage, or an irregular engine idle, book an appointment to have your oxygen sensor replaced. This will ensure your vehicle is running smoothly, efficiently, and will help prolong the life of your engine.
The statements expressed above are only for informational purposes and should be independently verified. Please see ourterms of servicefor more details
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