Oxygen Sensor Failures

New oxygen sensors have an average life duration. We suggest that the function of the sensor is tested every 20,000km or at a fixed period. After such mileages, the result is aged or defective sensors which have to be replaced. However, if they are prematurely defective, this means that your vehicle has some kind of problem. You must solve that problem immediately. The simple replacement of the oxygen sensor will not solve your vehicle's problem. Therefore, before replacing the oxygen sensor, ensure that the problem which has caused its early failure has been properly eliminated.

Failure	Causes	Effects
Oxygen sensor contamination by coolant antifreeze	Worn or damaged engine gaskets or components which cause coolant leakages in the exhaust. Ethylene glycol(antifreeze) of coolant contaminate the oxygen sensor.	Slower or missing sensor signal output. Head shows grey scaling over whitened metal
Oxygen sensor contamination by silicone	Silicone particulates in fuel or in the air/fuel mixture which contaminate the oxygen sensor.	Slower or missing sensor signal output. Sensor shows a fully whitened head.
Oxygen sensor contamination by lead	Bad quality fuel may still contain lead. Lead in the fuel mixture quickly contaminates the oxygen sensor	Slower or missing sensor signal output. Sensor head shows red-brownish metal
Oxygen sensor contamination by hydrocarbon depots	Faulty idle air control electrovalves or stepper motors, faulty pressure sensors or other engine management components cause a too rich mixture, which contaminates the oxygen sensor	Slower or missing sensor signal output. Sensor head shows black hydrocarbon deposits.
Oxygen sensor contamination by oil fumes	Worn out piston rings, worn or damaged engine gaskets or components which cause oil blow-by or leakages in the exhaust. Oil fumes contaminate the oxygen sensor	Slower or missing sensor signal output. Sensor head shows greasy oil deposits.
Oxygen sensor signals modified by bad electrical connection	Moisture or dirt in the sensor connector, as well as poor or incorrect wiring connection of the "universal" sensors, loss of grounding of 3-wire sensors due to corrosion or dirt on threading, etc. cause electrical problems which affect both the sensor and eventually the engine electronic control unit	The sensor works with a shifted characteristic, or incorrect signal levels; or gives no signal output. Further damage may result to the sensor itself or even the vehicle electronic control unit.
Overheated oxygen sensor	Defective ignition module, incorrect ignition timing, excessive spark advance, causes pre-ignition and engine knocking, with power loss. The exhaust has reached a too high temperature and overheated the sensor.	The sensor is damaged and gives no more signal output. Overheating effects are visible over the sensor head.
Fracture of oxygen sensor ceramic substrate	Cold water upon a very hot oxygen sensor may cause a sudden cooling of the sensor, which is transmitted to the inner ceramic substrate and causes its fracture.	The sensor is damaged and gives no more signal output. Broken ceramic inside and other effects over the sensor head can be noticed.
Oxygen sensor damaged by external cause	Road debris or stones which hit an oxygen sensor fitted below the vehicle, or any other hard mechanical shock, damage the sensor case or cable causing short or interruption of the wiring harness.	The sensor is damaged and gives no more signal output. The effects over the sensor case and/or the electrical harness can be noticed.