The oxygen sensor indirectly reflects the concentration of the mixture into the cylinder, and this information is transmitted to the electronic control unit (ECU) by fluctuating voltage, so the main method to judge the performance of the oxygen sensor is to detect the signal voltage value of the output of the oxygen sensor and its fluctuation range and fluctuation frequency. On the other hand, the engine can only activate the oxygen sensor if it reaches a certain temperature.
Detection methods for oxygen sensors
⑴ Detection by working conditions: The signal voltage output by the oxygen sensor (referring to the voltage of the connector terminal on the ECU wire side to the ground) should meet the following requirements: a. When the ignition switch is in the ON position, the signal voltage is approximately 0V; b. When the engine is idling with a cold engine, the signal voltage is approximately 0V; c. When the engine is idling after preheating, the signal voltage is approximately 0 V~1.0V; d. When the engine is accelerating after preheating, the signal voltage is approximately 0.5 V~1.0V; e. When the engine is decelerating after preheating, the signal voltage is approximately 0 V~0.4V.
⑵ Sensitivity detection: Start the engine and let the engine run at 2500 r/min for 3 minutes to allow the oxygen sensor to reach the operating temperature. The engine continues to run at 2500r/min, and the signal voltage of the oxygen sensor is measured at the same time. If the number of times the signal voltage fluctuates between 0.1 V~1.0V is greater than 8 times within 10 seconds, it means that the sensitivity of the oxygen sensor is normal. Otherwise, the oxygen sensor should be replaced.
⑶Simulation test: unplug an engine vacuum hose to simulate the mixture becoming thinner. If the signal voltage of the oxygen sensor drops to 0.1 V~0.3V; block the air filter inlet to simulate the mixture becoming thicker. If the signal voltage of the oxygen sensor rises to 0.8 V~1.0V, it means that the oxygen sensor is working properly. If the signal voltage of the oxygen sensor does not change as mentioned above, it means that the oxygen sensor is faulty and should be replaced.
