Oxygen sensors are essential components in engines that use three-way catalytic converters to reduce exhaust pollution. As the air-fuel ratio of the mixture deviates from the theoretical air-fuel ratio, the purification capacity of the three-way catalyst for CO, HC and NOx will be sharply reduced, so the oxygen sensor is installed in the exhaust pipe to detect the concentration of oxygen in the exhaust gas, and sends a feedback signal to the ECU, and then the ECU controls the increase or decrease of the fuel injection of the injector, so that the air-fuel ratio of the mixture is controlled near the theoretical value.
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.
