What happens to a car when the oxygen sensor is bad?

The car oxygen sensor, also known as the lambda probe, has the role of determining the level of oxygen in the exhaust gases emitted and then transmitting these data to the central unit of the vehicle computer (ECU) for interpretation. Any problem existing at the level of the emissions is noticed and immediately signaled by the electronic control unit (ECU).

Like any electronic component of a system, the oxygen sensor can be damaged. If it goes bad, the effects will be observed in the car’s behavior, such as increased fuel consumption, errors in the interpretation of emissions, and other engine problems.

To be able to diagnose such a problem, we describe below the most common signs that may indicate a malfunction in the oxygen sensor.

What is an oxygen sensor or lambda probe?

The lambda probe or oxygen sensor has the role of determining the level, but also the concentration of oxygen in the gas or liquid environment. Since 1980, this sensor has become an important part of all cars, which fulfills the role of gathering information about the available oxygen for combustion.

This information is transmitted further to the engine management system, which uses this data to adjust the injection. The importance of the sensor is given by its ability to contribute to achieving ideal engine performance, reducing fuel consumption, but also providing information on the resulting emissions.

By evaluating them, the probe can determine when the emissions exceed the required standards, the problem signaled by the “Check engine” light, and that of the probe. As a result of the improper operation caused by a faulty probe, the performance of the car decreases, and the fuel consumption increases, but problems also arise when interpreting the emissions.

If the probe is faulty, the computer will not be able to properly evaluate the ratio of air to fuel at the engine level. Oxygen is essential for the operation of the car, but its contribution may differ depending on the ambient temperature, altitude, engine temperature, barometric pressure. When it fails, the probe will not stop working altogether but will record lower and lower performances.

Why oxygen sensor is needed?

The problem of environmental pollution has led car manufacturers to find an effective solution to reduce the emissions of gases released into the atmosphere. Incomplete flue gas is one of the largest sources of pollution in the world, so for more than 25 years now, specialists have developed the sensor called oxygen sensor (Lambda Probe). Today, technology allows the well to reduce up to 90% of toxic gas emissions into the air.

It can measure the amount of oxygen released from the combustion process of the engine, but it also ensures the efficiency of the catalyst and reduces the emission of pollutants. When the car is running at high speed, the system is automatically deactivated to prevent depletion of the air and fuel mixture and to maintain a constant travel speed. The Lambda probe will order the engine to inject more gas until the mixture is suitable for the momentum of the engine.

If the Lambda probe detects too much oxygen in the exhaust gas, it means that the engine is running on too poor a mix, so it will increase the amount of fuel consumed, and if it detects too little oxygen, it means that the mix is too poor and the ECU will reduce of spent fuel.

When should the oxygen sensor be changed?

Specialists in the automotive field recommend checking the oxygen sensor every 30,000 km(19000 miles) you travel or every two to three years of the car’s operation, but also its immediate change if problems with its operation are noticed. Also, if you notice that the car has suddenly started consuming more fuel than it used to, it is most likely the probe, which announces a malfunction.

It may also be a malfunction when sealing the air intake or vacuum control circuits, also known as “fake air”, which misleads the oxygen sensor.
It gets to pass the information to the ECU that the mixture is too poor.

Thus, more gasoline will be pumped, and the engine will run on the exhaust or detonate, which will soon lead to premature wear and deterioration of the catalyst. So do not ignore the signs that your car gives you and schedule a visit to the car service as soon as possible, where the specialists can diagnose correctly and guide you to buy oxygen sensors suitable for the car model you are driving.

Types of oxygen sensors

There are five types of oxygen sensors, fundamentally different. Depending on each type, the probes vary concerning the ceramic element, the heating element, and the protection tube.

1. Underheated oxygen sensor.

The first type of o2 sensor appeared, this was for the first time manufactured in 1976 by the company Bosch and is characterized by a ceramic element with zirconium dioxide, ideal for generating a voltage in an environment with a high gas content, ie where oxygen is insufficient.

2. Heated oxygen sensor.

The Bosch company also released this type of probe, which is characterized by a heating element, ie a resistance, especially located inside the sensor, which facilitates reaching an optimum operating temperature in a maximum of 60 seconds.

3. Planar oxygen sensor

Bosch company continued to improve the wells produced, introducing in the market in 1997 this type of oxygen sensor, which, unlike the models that were launched before, uses sensory technology and is much more expensive than the others, from where it takes its name. The Planar oxygen sensor is made of ceramic and zirconium dioxide.

4. Planar oxygen sensor with broadband.

This is the latest oxygen sensor design and provides the engines with the accuracy required to meet the latest emission requirements. For their production, a planar ceramic element and zirconium dioxide are used as well, a combination that helps reduce emissions in the case of cold starting and heating the sensors much faster. This type of oxygen sensor is used in newly developed engines that allow direct fuel injection.

5. Oxygen sensor with titanium

Unlike other types, it uses a different type of oxygen sensing technology that, instead of generating a voltage signal that changes with the ratio of oxygen to fuel, changes the resistance of the sensor. Oxygen sensor with titanium is used on less than 0.5% of the cars in the world that have this type of sensor.

Common problems and symptoms of a bad oxygen sensor.

1. Check engine light stays on

The check engine light may remain on the dashboard as a result of several possible faults. One of the possibilities is represented by the incorrect functioning of the oxygen sensor. If the sensor transmits incorrect data or does not transmit any data, then we will notice that the light remains on.

2. Increases fuel consumption

If the O2 sensor is bad, the engine will suffer in the sense that the failure can result in increased fuel supply at the engine level and an incorrect air-fuel ratio. Therefore, fuel consumption will increase and the number of kilometers traveled will decrease considerably.

3. The engine does not work properly

Modifying the air-fuel ratio will destroy the balance necessary for the proper functioning of the engine. We will notice that the car will emit black smoke, but we will notice a different idling.

What can you do if the oxygen sensor no longer works?

Sensors of this type are small parts so changing them should not pose particular problems.
The first step you need to do to diagnose a problem and resolve it is to use an OBDII scanner. The scanner is an excellent device, necessary for any driver who owns a personal vehicle, a device that is capable of detecting any problems and displaying them.

It is advisable to check the car using the original OBD 2 scanner. Also, there are excellent alternatives to ODB2 scanners. We use this ODB2 scanner in our repair shop it’s doing a great job, also you can try this OBD2 alternative instead

If a sensor does not work properly, this information is transmitted to the ECU which will cause the Check Engine LED to illuminate on board. With the help of the scanner you can read and interpret the error code that appeared, and you can find out what is the cause that led to the problem.
If, after resetting the error code, the problem disappears, this means that you can postpone the visit to the service.

Voltmeter and test probe with clamp

You can use these parts to perform a direct test without disconnecting the sensor. It is necessary first of all to realize that the wires connecting the sensor are integral. If you have checked and everything is in order, start the engine and let it run. Connect the voltmeter to the sensor in question. If you do not do well, it is better to go to a service to do the rigorous testing.

Where is the oxygen sensor located?

correct position of the oxygen senzor

Each car has several O2 sensors that can be located at the exhaust flow level, at different levels – before the catalytic converter and after the converter.

Mounting at different levels allows the evaluation of the efficiency of the catalytic device (by the fact that certain parameters are analyzed before and after). The exact position of the sensors can be determined by consulting the technical book of the car.

How much does an oxygen sensor cost?

The price of a part varies depending on the make and model of your car and starts from 20 $. But you must also consider the price of the probe change operation. To get a correct offer, inform yourself before going into service. Choose the right service depending on the price but especially on customer recommendations and reviews.

How to replace an oxygen sensor?

Due to the difficult access position and the small size, the replacement or repair work is quite difficult. Frequent problems can also occur on the sensor connection cables, so it is good to check their integrity periodically. The advice of the specialists is to replace the oxygen sensor after several thousand km have been made, even if we have changed the oil. Most of the time, the oxygen sensor requires replacement after traveling 50,000 to 70,000 km (between 31000 and 43000 miles).

Monitor the condition of your vehicle periodically through service visits, to ensure that any problems are diagnosed early and remedied accordingly.

To replace the oxygen sensor with a new one, it is advisable to follow these steps:

  • 1. Determine precisely the position of the probe to be changed;
  • 2. Check the technical book to find the exact location;
  • 3. The probe is similar in appearance to a spark plug;
  • 4. Remove the screws that secure it in position;
  • 5. Check if the old oxygen sensor and the new one are identical;
  • 6. Mount the new o2 in position;
  • 7. Tie the wires/cables in the appropriate positions at the piece level;
  • 8. Put the key in the ignition, without starting the engine;
  • 9. Use the scanner to clear the error code;
  • 10. Start the engine;
  • 11. Check if the problem persists.

How do you check an oxygen sensor?

If the computer detects a fault in the O2 sensor, the Check Engine warning light will illuminate on the board. There may also be a message warning us that the heater circuit is not operating properly. The fact that these two warnings appear simultaneously can be interpreted as a problem in the oxygen sensor.

If you have basic information about what an oxygen sensor is and how it works, you can further document how to replace this part in the event of a malfunction. But if you do not have a minimum of knowledge, it is advisable to use the services of a mechanic to carry out the testing and repair in the case.

If you choose to change the sensor yourself, you must follow a few steps:

  • Use a 10-megawatt digital measuring device in the testing process. Using the information in the technical book, find out exactly the position of the probe and determine exactly which probe is defective according to the diagnostic error code (DTC).
  • Select a sensor to start testing. Start the car and let it run for about 20 minutes, then stop the engine. If necessary, lift the car off the ground using a car lift. Set the voltmeter to DC millivolts. Be careful not to come in contact with high-temperature surfaces generated by engine operation.
  • Connect the red wire to the signal cable, and the black wire to the table. Start the engine and check the voltage indicated by the voltmeter.
  • This is usually between 0.1 – 0.9 V. If the values are not included in this range, the probe may be defective or the engine may not operate as standard.
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