How to test a lambda probe with a tester?

2024 Author: Erin Ralphs | [email protected]. Last modified: 2024-02-19 11:41

Modern car has a fairly complex device, and the engine 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 another important element. This is a lambda probe. What is this sensor and how to check it? Consider in our today's article.

Characteristic

Lambda probe is a small piece of equipment that measures the amount of residual oxygen in a car's exhaust gases. It is also called an oxygen sensor. It is located behind the exhaust manifold. Access to the sensor is carried out 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 related toyourself. In the event of a malfunction of at least one of them, incorrect signals will be sent to the electronic engine unit. The system will prepare a deliberately wrong mixture with an increased or, conversely, a reduced concentration of gasoline.

Pay attention

An important condition for the operation of the sensor is the high temperature of the ceramic tip. It starts to analyze the concentration of oxygen ions at 300-400 degrees Celsius. Therefore, during warm-up, the ECU is guided by the average parameters before the tip heats up. But in recent years, the lambda probe has changed. So, often it is equipped with a heater. It is powered by 12 V.

Reasons for diagnosis

Before you check 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:

• Dips during car acceleration.
• Jerks when trying to pick up speed.
• Unstable engine idling.
• Increased fuel consumption.
• Check engine light on instrument panel.

If at least one of the above malfunctions occurs, this is an occasion for a more detailed check of the lambda probe sensor by a tester. But there are several diagnostic methods. We will consider them further.

Verification options

There are several methods on how to test a lambda probe:

• Heater he alth diagnostics.
• Check availabilityreference voltage.
• Lambda signal diagnostics.

The first two are the easiest. And to check the signal of the sensor, for this you need a pointer, not a digital tester.

Determine the voltage in the heating circuit

How to check the lambda probe? For this we need a multimeter. It needs to be converted to voltmeter mode. After that, you should warm up the engine so that its temperature is 80-90 degrees. Next, we turn off the engine, do not turn off the ignition and do not disconnect the probe connector (the system can write this to memory as an error). We check the voltage at the battery itself first. It must be at least 12 volts. The positive wire to the heater goes through a fuse or relay. We find it in the circuit and connect the multimeter probes. You also need to find the "mass". It is supplied from the engine ECU. If there is no voltage on the terminals (less than 12 volts), one of the contacts in the connector is most likely lost. We need to find an open circuit and fix it.

You can also find out what resistance the probe heater has. How to test a lambda probe? With the tester, we switch to the resistance measurement mode and measure this indicator between the heater wires. The resistance level should be at least two and no more than ten ohms. Otherwise, there was a break in contacts. Such a sensor needs to be replaced.

Determine the reference voltage

How to check the lambda probe with a multimeter? To do this, we transfer the device back to the voltage measurement mode. We turn on the ignition on the car. It is not necessary to warm up the sensor. Next, we measure the voltage between the negative and signal wires. The indicator should be about 0.45 volts.

Allowable run-up is 0.2 Volts. If this error is greater than normal, most likely the sensor has poor contact with ground, or there is a problem in the signal circuit.

Probe Signal Diagnosis

This is the most difficult operation. To do this, we need a motor tester, or a voltmeter with a pointer. Diagnostics 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 idle for three to five minutes. Then we connect the negative probe of the tester to the engine case. We determine the contacts of the sensor (there may be one, two or four). We connect the positive terminal of the tester probe to the signal wire. The voltage on the element should be from 0.2 to 0.9 volts and turn on at a frequency of eight to ten times in ten seconds. If the voltage is 0.45 volts and does not change, the element is most likely defective and needs to be replaced.

Please note: the voltage during diagnostics must vary over a wide range. If this indicator fluctuates around 0.3-0.7 Volts, most likely the element is defective.

It is also necessary to check the battery voltage on the heater power supply chip with the tester (the process is described above). It is the heater that can cause the malfunction.lambda probe. It will not be superfluous to check its grounding.

Norms of values

If the sensor is warm 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 suddenly closed, the voltage on the tester should drop to zero.

Specialists say that an 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 test a lambda probe with 4 wires?

Such devices are often found on Mercedes and Volkswagen cars. How to test a 4-wire oxygen sensor? First you need to measure the resistance level at the heater contacts. Two white wires are responsible for it. Between them, the nominal resistance should be about five ohms. After that, we pick up a multimeter and connect the positive probe to the signal output. At the same time, 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, we measure the voltage. After this time, it should be from 0.3 to 1 Volt. Please note that on a four-pin sensor, run-up in narrow ranges is also not allowed. If the voltage is from 0.4 to 0.5 Volts, then the element has become unusable.

How to test a lambda probe alone? If ayou have a mechanical throttle, you can just pull the cable on the intake manifold. If the car is equipped with an electronic gas pedal, you will definitely need an assistant who will hold and, if necessary, release the accelerator at your command.

Summing up

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 requires certain devices. At a minimum, tests should be done with a multi- or voltmeter. And for more detailed diagnostics, you will need an oscilloscope.