How does an oscilloscope test an oxygen sensor
Role --- changes in the oxygen content of the exhaust can cause the oxygen sensor voltage signal in the operating voltage value range of non-stop jump. The engine control voltage receives the oxygen sensor signal voltage, according to this voltage value to judge the state of the mixture, so as to adjust the injection pulse width. This is a simple statement. The role of the oxygen sensor is significant [fuel correction, catalytic converter monitoring, emissions monitoring, oxygen sensor monitoring -----].
Oxygen sensor abnormalities, caused by the failure is multi-faceted, fault performance symptoms are not the same, depending on the location of the fault, the size of the signal value, the model of the control strategy ----- and different. The following is to say that the oxygen sensor to determine the fault method
Oxygen sensor performance check is divided into three cases, one is to detect the sensor resistance; the second is to measure the oxygen sensor voltage output signal changes; the third is to observe the oxygen sensor appearance of the colour.
(1) Check the oxygen sensor resistance. When the engine temperature reaches normal, unplug the wire connector of the oxygen sensor, use the resistance meter to detect the resistance value between the terminals of the pressure sensor, the resistance value should meet the requirements of the standard value of the specific model (generally 440Ω), such as the resistance value is not in line with the requirements, it should be replaced with the oxygen sensor.
(2) the oxygen sensor voltage output signal detection, is installed in the oxygen sensor wire connector, from the signal terminal lead a wire, start the engine, so that the engine reaches the normal operating temperature, and maintain the engine idling. At this time, use a voltmeter to detect the output voltage of the oxygen sensor signal terminal. When unplugging a cylinder of the high-pressure ignition line (flameout), the oxygen content of the exhaust will fall, if the voltmeter indicates a rise in the voltage, indicating that the sensor performance is good (oxygen sensor output voltage is generally between 0.20.9V, and its range of variation in the range of 0.5V or so).
(3) in the oxygen sensor inspection, sometimes by observing the oxygen sensor top colour can also know the cause of failure. The normal colour of the oxygen sensor tip is light grey. Once the colour of the oxygen sensor tip is found to have changed, it is a sign that the oxygen sensor is faulty or at risk of failure.
a.The oxygen sensor with a black top is caused by carbon contamination, and after removal, the carbon deposits on it should be removed.
b. If the oxygen sensor is found to have a white top, this indicates that it is caused by silicon pollution, which is due to the engine in maintenance, the use of non-compliant silicon sealant, at this time, the oxygen sensor must be replaced.
c. When the oxygen sensor is found to have a reddish brown top, it means that the oxygen sensor is contaminated by lead, which is caused by the use of leaded petrol in the car.
Any silicone sealant that contains acetic acid (which acts as a vulcanising agent) will damage the oxygen sensor. Silicone is also called room temperature vulcanising (RTV) adhesive. Silicone containing acetic acid, if used in areas on the engine where lubricating oil flows, the acetic acid will evaporate into the crankcase or valve area, and then through the exhaust gas recirculation system into the intake pipe, and then under normal operating conditions, it will be discharged through the engine by the exhaust pipe, thus damaging the oxygen sensor.
Oxygen sensor as an important part of electronically controlled fuel injection engine, the normal operation of the engine and the effective control of exhaust emissions plays a vital role, once the oxygen sensor and its connecting lines failures, not only will make the emissions exceed the standard, but also deteriorate the engine operating conditions, resulting in idling stalling, engine operation inaccuracy, and other malfunctions. Therefore, timely monitoring and observation of the oxygen sensor, to ensure that the car is running in good condition, very useful.
1 Oxygen sensor failure will generally light up, the engine will be shaking, the exhaust has a sudden sound, there is a pungent odour, fuel consumption will increase, you can use the fault diagnostic instrument to detect the voltage, generally between 0.1-1 volts constantly changing, the number of changes in 10 seconds more than 8, if the voltage varies between 0.1-0.5 volts, indicating that the mixture is too dilute, if between 0.5-1 volts, indicating that the mixture is too thick! If the voltage varies between 0.1-0.5 volts, the mixture is too lean, and if it varies between 0.5-1 volts, the mixture is too rich.
2 How to identify the oxygen sensor good or bad
The actual application of the oxygen sensor has a zirconium oxide oxygen sensor and titanium oxide oxygen sensor two kinds, first check whether the oxygen sensor resistance is intact, unplug the oxygen sensor wiring harness, use the multimeter resistance gear to measure the oxygen sensor terminals in the heater terminal and the resistance between the lap bar, the resistance value of reference to the specific model specification. If it does not meet the standard, the oxygen sensor should be replaced. By observing the oxygen sensor top part of the colour can also determine the fault, 1 light grey top: this is the normal colour of the oxygen sensor. 2 white top: caused by silicon pollution, at this time the oxygen sensor must be replaced. 3 brown top: caused by lead contamination, if the seriousness of the oxygen sensor must also be replaced. 4 black top: caused by the accumulation of carbon in the engine to rule out the accumulation of carbon after the failure of the oxygen sensor can generally be automatically cleared! Carbon on the sensor
3 car oxygen sensor failure how to check judgement
The signal voltage of the oxygen sensor, as the most direct data reflecting the condition of the air-fuel ratio, is a very important reference data in fault diagnosis. Under the closed-loop condition, the working voltage of the oxygen sensor is generally 0.1-0.9 V. Usually, the maintenance personnel use the oscilloscope to detect or use the electronic control detector to read the corresponding data stream. These diagnostic equipment is not available in many small and medium-sized workshops.
