How To Use The Lambda Test To Determin Increasing Or Decreasing Returns
WHAT IS THE LAMBDA SENSOR'S Office?: FUNCTIONAL PRINCIPLE
Optimal combustion is required in order to ensure an platonic conversion rate of the catalytic converter. In the example of a gasoline engine, this is accomplished with an air-fuel ratio of 14.seven kg air to ane kg fuel (stoichiometric mixture). This optimum mixture is designated by the Greek alphabetic character λ (lambda). Lambda is used to express the air ratio between the theoretical air requirement and the bodily air flow supplied:
λ = supplied air flow : theoretical air flow = 14.7 kg : fourteen.7 kg = 1
Lambda sensor heating
The first lambda sensors were non heated, and and then had to be installed almost the engine in society to reach their operating temperature as quickly as possible. Nowadays, lambda sensors are equipped with sensor heating. This means that the probes can likewise be installed away from the engine.
Reward:
They are no longer exposed to the loftier thermal load. The sensor heating enables them to achieve their operating temperature within a short period, keeping the time in which the lambda control is not active to a minimum. Excessive cooling is prevented during idle way, when the frazzle gas temperature is not as loftier. Heated lambda sensors have a shorter response time, which has a positive effect on the control speed.
Utilize of multiple lambda sensors
Since the introduction of the EOBD, the function of the catalytic converter must also be monitored. An additional lambda sensor is installed behind the catalytic converter for this. This is used to make up one's mind the ability of the catalytic converter to shop oxygen.
The function of the probe downstream of the catalytic converter is the same equally the upstream probe. The amplitudes of the lambda sensors are compared in the control unit. The voltage amplitudes of the downstream probe are very small-scale due to the ability of the catalytic converter to shop oxygen. The lower the storage capacity of the catalytic converter, the college the voltage amplitudes of the downstream probe due to the increased oxygen content.
The heights of the amplitudes at the downstream probe are dependent on the actual storage capacity of the catalytic converter, which varies depending on the load and speed. The load condition and speed are therefore taken into consideration when comparing the probe amplitudes. If the voltage amplitudes of both probes are still roughly the aforementioned, the storage capacity of the catalytic converter has been reached, e.1000. through aging.
FAULTY LAMBDA OXYGEN SENSOR: SYMPTOMS
A faulty lambda sensor can crusade the following symptoms:
- High fuel consumption
- Poor engine functioning
- High exhaust emissions
- Engine indicator lamp comes on
- Error code is stored
Furnishings OF FAULTY LAMBDA OXYGEN SENSOR: Cause OF FAILURE
There are several reasons why a failure may occur:
- Internal and external brusk circuits
- No ground / voltage supply
- Overheating
- Deposits / contagion
- Mechanical damage
- Use of leaded fuel / additives
There are a range of typical lambda sensor faults that occur frequently. The following list shows the causes behind diagnosed faults:
Unheated probes
| Diagnosed faults | Crusade |
|---|---|
| Protective tube or probe body clogged with oil residues | Unburned oil has constitute its way into the exhaust system, east.g. due to faulty piston rings or valve stem seals |
| False air intake, lack of reference air | Probe installed incorrectly, reference air opening blocked |
| Impairment due to overheating | Temperatures above 950 °C due to incorrect ignition point or valve play |
| Poor connection at the plug contacts | Oxidation |
| Interrupted cablevision connections | Poorly routed cables, abrasion points, rodent bites |
| Lack of basis connection | Oxidation, corrosion at the exhaust system |
| Mechanical harm | Excessive tightening torque |
| Chemical aging | Brusque routes very oftentimes |
| Atomic number 82 deposits | Use of leaded fuel |
FAULT DIAGNOSTICS FOR THE LAMBDA OXYGEN SENSOR: BASIC PRINCIPLES
Vehicles that are equipped with cocky-diagnostics tin can detect faults occurring in the control circuit and store them in the fault retentiveness. This is usually displayed through the engine indicator lamp. The mistake retention can then be read out with a diagnostic unit of measurement for fault diagnostics. However, older systems are not able to determine whether this fault relates to a lacking component or e.g. a cablevision mistake. In this case, further tests must exist carried out by the mechanic.
Equally part of the EOBD, the lambda sensor monitoring has been expanded to include the following points:
- Open circuit,
- Operational readiness,
- Short excursion to command unit ground,
- Short excursion to positive
- Cablevision suspension and lambda sensor crumbling.
In order to diagnose the lambda sensor signals, the control unit uses the form of the signal frequency.
For this, the control unit calculates the following data:
- The maximum and minimum detected sensor voltage value,
- The fourth dimension between the positive and negative flank,
- Lambda controller regulating variable co-ordinate to rich and lean,
- Control threshold of the lambda control,
- Probe voltage and period duration.
CHECKING THE LAMBDA PROBE USING AN OSCILLOSCOPE, MULTIMETER, LAMBDA SENSOR TESTER, EMISSION ANALYSER: TROUBLESHOOTING
Equally a basic principle, a visual inspection should be carried out earlier each bank check to ensure that in that location is no harm to the cable or connector. The exhaust organization must not have any leaks.
It is recommended to use an adapter cable to connect the measuring device. It must also be ensured that the lambda control is not active during some operating states, east.1000. during cold start until the operating temperature is achieved, and when at full load.
Checking the lambda sensor with the exhaust tester
Exhaust tester
Ane of the quickest and easiest tests is to measure with the 4-gas emission analyser.
The test is carried out in the same style as the prescribed exhaust emissions test. With the engine is at operating temperature, false air is connected as a disturbance variable by removing a hose. 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 discover this from a certain value and conform it within a certain time (lx seconds, equally in the frazzle emissions test). If the disturbance variable is removed, the lambda value must exist 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 decide whether the lambda control is working. An electrical test is not possible. With this procedure, at that place is a risk that modern engine management systems control the mixture through precise load detection so that λ = 1, despite the lambda control not working.
Checking the lambda sensor with the multimeter
Multimeter
Merely high-impedance multimeters with digital or analog brandish should exist used for the examination.
Multimeters with a depression internal resistance (mostly in analog devices) overload the lambda sensor signal and may cause it to break down. Due to the chop-chop alternating voltage, the signal is all-time depicted with an analog device.
The multimeter is continued parallel to the betoken line (blackness cablevision, see circuit diagram) of the lambda sensor. The measuring range of the multimeter is gear up to 1 Five or 2 Five. After the engine is started, a value between 0.four – 0.6 V appears on the display (reference voltage). If the operating temperature of the engine or lambda sensor is reached, the fixed voltage begins to alternate between 0.one 5 and 0.nine Five.
In order to achieve flawless measuring results, the engine should be kept at a speed of approx. 2,500 rpm. 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 chance that the unheated probe cools down and a signal is no longer generated.
Checking the lambda sensor with the oscilloscope
Lambda sensor indicate pattern
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 continued to the signal line. The measuring range to exist set is dependent on the oscilloscope used. If the device has automatic signal detection, this should be used. For manual adjustment, gear up a voltage range of i – 5 Five and a time setting of i – 2 seconds.
The engine speed should once over again be approx. ii,500 rpm.
The alternating voltage appears on the brandish in sinusoidal form. The post-obit parameters can exist evaluated at this indicate:
- Aamplitude summit (maximum and minimum voltage 0.1 – 0.9 V),
- Response time and period duration (frequency approx. 0.v – 4 Hz).
Checking the lambda sensor using the lambda sensor tester
Lambda sensor tester
Diverse 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 continued to the signal line of the probe. Once the probe has reached operating temperature and begins working, the LEDs showtime to light upwards in alternation – depending on the air-fuel ratio and voltage curve (0.1 – 0.9 V) of the probe.
Here, all specifications for the measuring device settings for the voltage measurement chronicle 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.one – five V.
Checking the status of the protective tube
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 adequacy:
CHECKING THE LAMBDA OXYGEN SENSOR HEATING: TROUBLESHOOTING
The internal resistance and voltage supply of the heating chemical element can be checked.
For this, disconnect the connector to the lambda sensor. On the lambda-sensor side, utilize the ohmmeter to mensurate the resistance at both cables for the heating element. This should exist betwixt two and 14 ohms. On the vehicle side, use the voltmeter to measure the voltage supply. There must be a voltage > 10.5 V (on-board voltage).
Unlike connection options and cablevision colors
Unheated probes
| Number of cables | Cable color | Connection |
|---|---|---|
| one | Black | Signal (ground via housing) |
| 2 | Black | Signal Footing |
Heated probes
| Number of cables | Cable colour | Connection |
|---|---|---|
| 3 | Black 2 x white | Betoken (footing via housing) of heating element |
| 4 | Black two x white Grey | Signal, heating element, ground |
Titanium dioxide probes
| Number of cables | Cable colour | Connexion |
|---|---|---|
| 4 | Cerise White Black Yellow | Heating chemical element (+) Heating element (-) Betoken (-) Signal (+) |
| iv | Black ii x white Grey | Heating element (+) Heating element (-) Bespeak (-) Signal (+) |
(Manufacturer's specifications must be observed)
Changing THE LAMBDA OXYGEN SENSOR: VIDEO
How To Use The Lambda Test To Determin Increasing Or Decreasing Returns,
Source: https://www.hella.com/techworld/uk/Technical/Sensors-and-actuators/Test-lambda-sensor-4379/
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