1, oxygen sensor heater resistance check
Unplug the oxygen sensor harness connector and measure the resistance between the heater post and the grounding column of the oxygen sensor terminal with a multimeter resistance. The resistance is 4-40Ω (refer to the specific vehicle specification). If you do not meet the standard, you should replace the oxygen sensor.
2, oxygen sensor feedback voltage measurement
When measuring the feedback voltage of the oxygen sensor, pull out the wiring harness of the oxygen sensor, and draw a thin wire from the feedback voltage output terminal of the oxygen sensor, and then insert the harness connector. When the engine is running, (Some models can also be measured by the fault detection socket oxygen sensor feedback voltage, such as Toyota Motor Co., Ltd. can produce a series of cars from the fault detection socket OX1 or OX2 terminal directly measured oxygen sensor Of the feedback voltage).
When detecting the feedback voltage of the oxygen sensor, it is preferable to use a pointer type multimeter with a low range (usually 2V) and a high impedance (internal resistance greater than 10MΩ). Specific detection methods are as follows:
1): the engine hot car to the normal working temperature (or start to 2500r / min speed running 2min);
2): the negative voltage of the multimeter voltage meter connected to the fault detection socket E1 or battery negative, the table is connected to the fault detection socket OX1 or OX2 jack, or oxygen sensor harness connector on the number |
3): Let the engine to 2500r / min or so to maintain the speed of operation, and check the voltmeter pointer can swing back and forth between 0-1V, note the 10s within the voltage meter pointer swing the number of times. Under normal circumstances, with the feedback control carried out, the oxygen sensor feedback voltage will be 0.45V up and down constantly changing, 10s within the feedback voltage changes should be no less than 8 times. If less than 8 times, then the oxygen sensor or feedback control system is not working properly, the reason may be oxygen sensor surface carbon deposition, the sensitivity caused by lower. In this regard, the engine should be allowed to run at 2500r / min speed of about 2min, to clear the oxygen sensor surface carbon deposition, and then check the feedback voltage. If the barometer after the removal of the voltmeter pointer changes are still slow, then the oxygen sensor damage, or computer feedback control circuit is faulty.
3, check the oxygen sensor for damage
Unplug the oxygen sensor harness connector, so that the oxygen sensor is no longer connected with the computer, the feedback control system in the open-loop control state. Will be a multimeter voltage file is directly connected with the oxygen sensor feedback voltage output terminal connection, a good negative table pen. In the engine operation to measure the feedback voltage, the first off the inlet tube in the crankcase forced ventilation pipe or other vacuum hose, artificially form a lean mixture, while watching the voltmeter, the pointer reading should be reduced. And then connected to the disengagement of the pipeline, and then unplug the water temperature sensor connector, with a 4-8KΩ resistor instead of water temperature sensor, artificially form a thick mixture, while watching the voltmeter, the pointer reading should rise. You can also suddenly depress or release the accelerator pedal to change the concentration of the mixture, in the sudden step on the accelerator pedal, the mixture becomes thicker, the feedback voltage should rise; suddenly release the accelerator pedal, the mixture becomes thinner, The feedback voltage should drop. If the feedback voltage of the oxygen sensor does not change as described above, it indicates that the oxygen sensor is damaged.
In addition, the titanium oxide oxygen sensor in the use of the above method of detection, if a good oxygen sensor, the output voltage should be 2.5V as the center up and down fluctuations. Otherwise the sensor can be removed and exposed to air, after cooling to measure the resistance value. If the resistance value is large, indicating that the sensor is good, otherwise the sensor should be replaced.
4, oxygen sensor appearance color inspection
Remove the oxygen sensor from the exhaust pipe, check the sensor housing on the ventilation holes are blocked, ceramic core with or without damage. If damaged, replace the oxygen sensor. By observing the color of the top part of the oxygen sensor can also determine the fault:
① light gray top: This is the normal color of the oxygen sensor;
② white top: caused by silicon pollution, this time must be replaced with oxygen sensor;
③ brown top: caused by lead pollution, if serious, must also replace the oxygen sensor;
④ black top: caused by carbon deposition, in the exclusion of engine carbon deposition failure, the general can automatically remove the oxygen sensor on the carbon deposition.