How to Determine if the Oxygen Sensor is Faulty?
3 Answers
Methods to determine if the oxygen sensor is faulty: Observe the color of the oxygen sensor's tip. If the tip is white, it indicates that the oxygen sensor has been contaminated by silicon to a certain extent and needs to be replaced promptly. If it is brown, it is caused by lead contamination and also requires replacement. If the tip is black, it is mainly due to carbon buildup, and simply cleaning it thoroughly will suffice. The primary function of the automotive oxygen sensor is to enable the engine to obtain an optimal concentration of the air-fuel mixture, thereby reducing the emission of harmful gases and saving fuel. The oxygen sensor measures the oxygen content in the exhaust gases after engine combustion, converts the oxygen level into a voltage signal, and transmits it to the engine computer. This allows the engine to achieve closed-loop control based on the excess air factor, ensuring that the three-way catalytic converter efficiently converts and purifies the three major pollutants in the exhaust—hydrocarbons, carbon monoxide, and nitrogen oxides—maximizing the reduction of emissions.
I remember last year my car suddenly had ridiculously high fuel consumption, couldn't go more than a few days on a full tank, and the check engine light stayed on. When I took it to the repair shop, the mechanic said it might be an oxygen sensor issue. They connected the diagnostic tool to the car's computer, and sure enough, it showed oxygen sensor trouble code P0130. If you usually notice a rotten egg smell from the exhaust or unstable engine idle with shaking, nine times out of ten it's a failed oxygen sensor. When this part fails, it not only wastes fuel but can also damage the catalytic converter if left unattended for long. I suggest getting it checked early, unlike me who wasted hundreds on fuel before fixing it. After replacing the sensor, fuel consumption immediately returned to normal levels.
Last week, I helped my neighbor check his vintage car, which had a tachometer that fluctuated up and down like dancing at idle. I used a multimeter to measure the feedback voltage at the oxygen sensor connector and found the needle stuck around 0.2V without moving. Normally, it should rapidly fluctuate between 0.1V and 0.9V, clearly indicating the oxygen sensor has failed. Additionally, when I removed the exhaust pipe for inspection, I found the sensor tip covered in thick black carbon deposits that couldn’t even be cleaned off with carburetor cleaner. In fact, you can perform a simple check yourself: after the engine is warmed up, unplug the sensor connector—if the engine operation doesn’t change, it’s almost certain the sensor is faulty. This thing acts like the engine’s breathing monitor; if it fails, the whole car can’t 'breathe' properly.
