Akin's Auto Repair

Oxygen Sensors |O2 Sensor | Check Engine light Diagnostics

Your check engine light comes on to alert you of a fault with your vehicle. This could be for a number of reasons such as oxygen sensors, crankshaft/camshaft position sensors, thermostat, mass air flow sensor, engine misfires, engine vacuum leaks, etc. We are here to help! Stop by for a courtesy check engine light code scan and we can advise you on your next step. Trust Akins Auto Repair with your next auto Electrical Diagnostic & service. Contact us in San Jose(FREE scan for trouble codes 1996 and up vehicles only. Diagnostic charges may be additional)

Oxygen Sensors

What Does An Oxygen Sensor Do?

As a vehicle owner the last thing you want to see is the bright orange “Check Engine” light burning. This alert is almost always the result of a tripped oxygen, aka O2, sensor. Another warning sign could be the message on your car’s computer that there is a heater circuit malfunction. When you see

the Check Engine Light (CEL) or heater circuit malfunction message it could mean that your O2 sensor has simply gone bad. Of course, it could als

o mean that your vehicle is not running properly resulting in an excessive amount of emissions. Whatever the case, taking your vehi

cle in for a tune up is the best bet to ensure that your vehicle’s O2 sensor is in top performance.

What is an Oxygen Sensor?

The oxygen sensor, also known as a lambda sensor, was developed in the late 1960s by Dr. Gunter Bauman for the Robert Bosch GmbH company. This sensor is an electronic device used to measure the proportional amount of oxygen in a liquid or gas. The original oxygen sensor was made using ceramic coated zirconia and platinum. In order to make the O2 sensor more capable of mass production, planar oxygen sensors were developed. This modernized O2 sensor was developed by NTK in 1990 for use in the Honda Civic and Accord. Made using layers of High Temperature Cofired Ceramic (HTCC) green tapes, the current style of sensor is made more efficient than the original style sensors.

Common Symptoms of a Bad Oxygen Sensor

Poor Gas Mileage

Depending on the type and/or location of a faulty oxygen sensor, the fuel-delivery and the fuel-combustion systems can be thrown off or made irregular by a faulty oxygen sensor. If too much fuel is injected into an engine’s cylinders or a faulty oxygen sensor disturbs the delicate air/fuel mixture of an engine, gas mileage will suffer

Engine Missing

A bad oxygen sensor can impede the air/fuel mixture of an engine or interfere with the engine combustion, both of which can cause an engine to miss, or run irregularly. An engine miss is normally most pronounced at idle or at lower engine speeds; a faulty oxygen sensor can inhibit the normal fuel delivery/combustion within an engine and cause a miss.

Rough Engine Idle

Vehicle engines that have a bad oxygen sensor often run irregularly or roughly. Oxygen sensors can control or contribute to many different engine functions, including fuel/air mixture, engine timing and engine combustion intervals. A faulty oxygen sensor can disrupt any of these things and cause a rough engine idle.

When to replace Oxygen Sensors

Your vehicle’s oxygen sensors play an important role in the optimal operation of your vehicle, but these parts are often overlooked when performing regular vehicle maintenance. The main reason for this is because many automobile owners do not know the symptoms of bad oxygen sensors, and only learn of the issue when the check engine light sparks up on their dashboard or their vehicle fails an emissions test. The role of your oxygen sensor is simple; it performs tests on your car’s exhaust to determine how much oxygen is in it. It then transports the data to your vehicle’s computer, which uses the findings to create the perfect air to fuel mixture for optimal engine performance. On top of poor engine performance, a bad oxygen sensor will have an increased negative impact on the environment as it releases higher levels of pollution into the air

That is all fine and dandy, but you probably want to know when to an replace oxygen sensor on your car or truck.

O2 sensors are a relatively inexpensive part to replace on your vehicle. If you have a suspicion about your part being faulty, it is best to change it earlier than later. It is not very common for an O2 sensor to completely fail, as it more often fails over time. If you do not know failing oxygen sensor symptoms, you will not be able to diagnose the problem until it completely fails. In the meantime your vehicle will suffer from poor engine performance which can have long term effects on your engine life. Typically, mechanics have recommendations on the replacement intervals for these parts. Cars and Trucks from the 1970’s to 1990’s that were equipped with unheated one or two wire oxygen sensors should have the part replaced around the 45,000 mile mark. For automobiles that were manufactured in the 1980’s to 1990’s, and were equipped with heated three and four wire oxygen sensors, it is recommended you replace the part every 65,000 miles. All cars and trucks that were manufactured in the last fifteen years should have their O2 sensors replaced every 60,000 to 90,000 miles. Replacing your sensor at these intervals will lower the level of pollution that your vehicle emits while playing a preventive role in the cause of damage to the vehicle.

Every new car, and most cars produced after 1980, have an oxygen sensor. The sensor is part of the emissions control system and feeds data to the engine management computer. The goal of the sensor is to help the engine run as efficiently as possible and also to produce as few emissions as possible.

A gasoline engine burns gasoline in the presence of oxygen (see How Car Engines Work for complete details). It turns out that there is a particular ratio of air and gasoline that is “perfect,” and that ratio is 14.7:1 (different fuels have different perfect ratios — the ratio depends on the amount of hydrogen and carbon found in a given amount of fuel). If there is less air than this perfect ratio, then there will be fuel left over after combustion. This is called a rich mixture. Rich mixtures are bad because the unburned fuel creates pollution. If there is more air than this perfect ratio, then there is excess oxygen. This is called a lean mixture. A lean mixture tends to produce more nitrogen-oxide pollutants, and, in some cases, it can cause poor performance and even engine damage.

The oxygen sensor is positioned in the exhaust pipe and can detect rich and lean mixtures. The mechanism in most sensors involves a chemical reaction that generates a voltage (see the patents below for details). The engine’s computer looks at the voltage to determine if the mixture is rich or lean, and adjusts the amount of fuel entering the engine accordingly.

The reason why the engine needs the oxygen sensor is because the amount of oxygen that the engine can pull in depends on all sorts of things, such as the altitude, the temperature of the air, the temperature of the engine, the barometric pressure, the load on the engine, etc.

When the oxygen sensor fails, the computer can no longer sense the air/fuel ratio, so it ends up guessing. Your car performs poorly and uses more fuel than it needs to.

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