A modern car has a rather complicated device, and engine operation is not complete without a whole set of sensors. Among these, one can note the element responsible for the position of the crankshaft, throttle angle, antifreeze temperature and ignition timing. But there is one more important element. This is a lambda probe. What is this sensor and how to check it? Consider in our article today.
Characteristic
A lambda probe is a small mechanism that is designed to measure the amount of residual oxygen in the exhaust gases of a car. It is also called an oxygen sensor. It is located behind the exhaust manifold. Access to the sensor is from under the bottom, or from under the hood (depending on the type and design of the car).
Also note that there can be several such sensors in the system. One is installed behind the catalyst, the second after. Both elements are closely interconnected. In the event of a malfunction of at least one of them, incorrect signals will be sent to the engine electronic block. The system will prepare a deliberately wrong mixture with an increased or vice versa low concentration of gasoline.
note
An important condition for the operation of the sensor is the high temperature of the ceramic tip. He begins to analyze the concentration of oxygen ions at 300-400 degrees Celsius. Therefore, during warm-up, the ECU is guided by the averaged parameters before the tip is heated. But in recent years, the lambda probe has changed. So, often it is equipped with a heater. It runs on a 12 V network.
Reasons for diagnosis
Before checking the lambda probe sensor , you need to find out if the problems are really related to its malfunction. If this element breaks down, the driver may experience the following problems:
- Failures during acceleration of the car.
- Jerks when trying to gain speed.
- Unstable engine idling.
- Increased fuel consumption.
- The “Check engine” lamp on the instrument panel.
If at least one of the above faults occurs, this is an occasion for a more detailed check of the lambda probe sensor by the tester. But there are several diagnostic methods. We will consider them further.
Verification Options
There are several methods for checking a lambda probe:
- Diagnostics of heater performance.
- Check for voltage reference.
- Diagnostics of the lambda signal.
The first two are the simplest. And to check the sensor signal, for this you need a pointer, not a digital tester.
We determine the voltage in the heating circuit
How to check lambda probe? For this we need a multimeter. It needs to be put into voltmeter mode. After this, the engine should be warmed up so that its temperature is 80-90 degrees. Then we turn off the engine, do not turn off the ignition, and do not disconnect the probe connector (the system may write this to memory as an error). We check the voltage first on the battery itself. It should be at least 12 volts. The positive wire to the heater fits through a fuse or relay. We find it in the circuit and connect the probes of the multimeter. You also need to find the "mass". It is supplied with an engine ECU. If there is no voltage at the terminals (less than 12 volts), most likely one of the contacts in the connector has been lost. It is necessary to find an open circuit and repair it.
You can also find out what resistance the probe heater has. How to check lambda probe? The tester switches to the resistance measurement mode and measures this indicator between the heater wires. The resistance level must be at least two and not more than ten ohms. Otherwise, contact breakage has occurred. Such a sensor needs to be replaced.
Determine the reference voltage
How to check a lambda probe with a multimeter? To do this, put the device back into voltage measurement mode. Turn on the ignition on the car. Warming up the sensor is not necessary. Next, measure the voltage between the negative and signal wires. The indicator should be about 0.45 volts.
Allowable takeoff - 0.2 Volts. If this error is greater than the norm, most likely the sensor has poor contact with the ground, or there is a problem in the signal circuit.
Probe Signal Diagnostics
This is the most difficult operation. To do this, we need a motor tester, or a voltmeter with an arrow pointer. Diagnosis is as follows. Before checking the lambda probe, at the first stage it is necessary to warm up the device to operating temperatures. To do this, turn on the engine and let it run idle for three to five minutes. Then we connect to the engine housing the negative probe of the tester. We determine the contacts of the sensor (there can be one, two or four). We connect the positive output of the tester probe to the signal wire. The voltage on the element should be from 0.2 to 0.9 Volts and turned on with a frequency of eight to ten times in ten seconds. If the voltage is 0.45 Volts and does not change, most likely the element is defective and needs to be replaced.
Please note: the voltage during diagnosis should vary over a wide range. If this indicator fluctuates around 0.3-0.7 Volts, most likely the element is faulty.
Also, the tester needs to check the battery voltage on the heater power supply chip (the process is described above). It is the heater that can cause the malfunction of the lambda probe. Checking its grounding will not be superfluous.
Norms of Values
If the sensor is warmed up and working properly, the voltage level at the signal output should be from 0.2 to 1 Volt at engine speeds of 2.5 thousand per minute.
When you sharply press the gas pedal, the device should show exactly 1 volt of voltage. When the throttle is abruptly closed on the tester, the voltage should drop to zero.
Experts say that the oscilloscope will be the most accurate in this diagnostic operation. The cost of this device is about one and a half to two thousand rubles.
How to check a lambda probe with 4 wires?
Such devices are often found on Mercedes and Volkswagen cars. How to check an oxygen sensor with four wires? First you need to measure the resistance level at the contacts of the heater. Two white wires are responsible for it. Between them, the nominal resistance should be about five ohms. After that, take a multimeter in our hands and connect the positive probe to the signal output. In this case, we spin the engine up to three thousand revolutions. Hold the pedal for a couple of minutes. How to check the lambda probe VAZ? Without releasing the gas pedal, measure the voltage. After this time, it should be from 0.3 to 1 Volt. Please note that the four-pin sensor is also not allowed to run in narrow ranges. If the voltage is from 0.4 to 0.5 Volts, it means that the element has become unusable.
How to check lambda probe one? If you have a mechanical throttle actuator, you can just pull the cable on the intake manifold. If the car is equipped with an electronic gas pedal, you definitely need an assistant who will hold the accelerator at your command and, if necessary.
To summarize
So, we found out what a lambda probe is and how to test it in several ways. As you can see, the operation is simple, but it requires certain devices. At a minimum, tests need to be done with a multi- or voltmeter. And for a more detailed diagnosis, an oscilloscope is already required.