How to Measure a Four-Wire Oxygen Sensor?
2 Answers
The measurement method for a four-wire oxygen sensor is: 1. Start the engine; 2. Increase the throttle to reach 1500 RPM, then test the signal voltage of the oxygen sensor—the voltage should be between 0.1 and 0.9 volts for normal operation; 3. Measure the resistance between the two wires, which should be around 10 ohms. The function of the oxygen sensor is to convert oxygen content into a voltage signal and transmit it to the engine computer, enabling the engine to achieve closed-loop control targeting excess air. The working principle of the oxygen sensor is: using a ceramic sensing element to measure the oxygen potential in the car's exhaust pipe, calculating the corresponding oxygen concentration based on the chemical equilibrium principle, thereby monitoring and controlling the combustion air-fuel ratio to ensure product quality and compliance with exhaust emission standards.
Measuring the four wires of an oxygen sensor is actually quite simple. I would set the multimeter to the resistance range, first unplug the sensor connector, and measure the resistance of the heater wire (white wire), which should normally be around 4-15 ohms. For the signal wires, the black and gray wires correspond to the front and rear oxygen sensors. Connect them to the multimeter set at 20V range, start the engine, and observe if the voltage fluctuates between 0.1-0.9V. Remember, it's crucial to let the engine warm up fully; cold engine measurements won't be accurate. If the voltage remains fixed, the sensor is faulty. For the ground wire, just check for continuity. Last time, my neighbor's car threw a trouble code, and after testing like this, we found a short in the heater wire. Replacing the sensor fixed the issue.
