This sensor helps to determine whether this air-fuel ratio is lean or rich. Volvo and Saab were the first to use Lambda Sensor. By the year , this sensor was implemented in almost all the gasoline vehicles in Europe. There are two parts in Lambda Sensor — Sensor that gets heated and the heating sensor. The heating sensor helps the Lambda sensor in reaching its operating temperature. When the engine reaches the right temperature, the sensor starts measuring the unburnt oxygen present in the exhaust gases.
This output is sent to the computer unit where it calculates the air-fuel ratio and checks the look-up table to optimize this air-fuel ratio. Based on this information, a calculated amount of fuel required by the engine to burn at a stoichiometric ratio is released, ensuring complete combustion. Through the changing exhaust gas composition, the lambda value that is calculated and displayed by the exhaust tester also changes. The mixture formation system must detect this from a certain value and adjust it within a certain time 60 seconds, as in the exhaust emissions test.
If the disturbance variable is removed, the lambda value must be reduced to the original value. As a basic principle, the specifications for disturbance variable connection and the lambda values of the manufacturer should be observed. However, this test can only determine whether the lambda control is working. An electrical test is not possible. Multimeters with a low internal resistance mostly in analog devices overload the lambda sensor signal and may cause it to break down.
Due to the quickly alternating voltage, the signal is best depicted with an analog device. The multimeter is connected parallel to the signal line black cable, see circuit diagram of the lambda sensor. The measuring range of the multimeter is set to 1 V or 2 V. After the engine is started, a value between 0. If the operating temperature of the engine or lambda sensor is reached, the fixed voltage begins to alternate between 0. In order to achieve flawless measuring results, the engine should be kept at a speed of approx.
This ensures that the operating temperature of the probe is reached, even in systems with an unheated lambda sensor. If the exhaust gas temperature is not sufficient in idle mode, there is a risk that the unheated probe cools down and a signal is no longer generated.
The lambda sensor signal is best depicted using the oscilloscope. As for the measurement with the multimeter, a basic prerequisite is that the engine or lambda sensor must be at operating temperature. The oscilloscope is connected to the signal line. The measuring range to be set is dependent on the oscilloscope used. If the device has automatic signal detection, this should be used. For manual adjustment, set a voltage range of 1 — 5 V and a time setting of 1 — 2 seconds. The alternating voltage appears on the display in sinusoidal form.
The following parameters can be evaluated at this signal:. Various manufacturers offer special lambda sensor testers for testing. With this device, the function of the lambda sensor is displayed via LEDs.
Like the multimeter and oscilloscope, it is connected to the signal line of the probe. Once the probe has reached operating temperature and begins working, the LEDs start to light up in alternation — depending on the air-fuel ratio and voltage curve 0.
Here, all specifications for the measuring device settings for the voltage measurement relate to zirconium dioxide sensors voltage jump sensors. For titanium dioxide, the voltage measuring range changes to 0 — 10 V, with the measured voltages alternating between 0. The manufacturer's specifications must be observed as a basic principle. Alongside the electronic test, the condition of the probe element protective tube may give an indication about the functional capability:.
The probe should be exchanged and the cause for the excessively rich mixture remedied, to prevent the probe from becoming sooted again. The lead destroys the probe element. The probe must be replaced and the catalytic converter checked.
Replace the leaded fuel with unleaded fuel. Improper mounting may damage the lambda sensor such that proper functioning cannot be guaranteed. During mounting, the prescribed special tool must be used and the tightening torque observed. For this, disconnect the connector to the lambda sensor. On the lambda-sensor side, use the ohmmeter to measure the resistance at both cables for the heating element.
This should be between 2 and 14 ohms. On the vehicle side, use the voltmeter to measure the voltage supply. AE Newsletter Video. Toggle navigation. Home Technical. Compact knowledge: From basic knowledge to diagnostic tips for professionals — these pages provide you with HELLA expertise for your day-to-day work.
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Functional principle. Cause of failure. Basic principles. Voltage jump probe. Resistance jump probe. Fitted in both petrol and diesel vehicles, they help to reduce the number of harmful emissions, primarily gases such as carbon monoxide, and pollutants, produced by your car. The sensors are designed to work within government exhaust gas legislation.
Due to the role they play in the operation of your car, they are also widely known as oxygen sensors or O2 sensors. When your car burns petrol or diesel, it mixes it with air to provide the most efficient operation of your engine.
This ratio of air to fuel is known as the stoichiometric ratio. Or, and much easier to pronounce, the lambda ratio. With fuel that runs rich, there is excess, unburned fuel. A lean fuel mix tends to produce more nitrogen-oxide pollutants. It can also cause poor engine performance and possible engine damage. In modern cars, there are often 2 sensors. The first is directly after the engine and before the catalytic converter. The second is placed after the catalytic converter to monitor the overall operation.
It also checks that your cat is doing is its job correctly. Your lambda sensor converts the amount of oxygen present in your exhaust into an electric signal and sends the signal to the computer that controls your engine operation.
The ECU engine control unit processes the readings and sends the information back to the engine. The engine then makes compensations of how to mix fuel and air to get the ratio back to where it needs to be. The voltage your sensor creates operates between 0.
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