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 fixed period. After such mileages, they result aged or defective and have to be replaced. However, if they are prematurely defective, this means that your vehicle has some problem. You must solve that problem immediately. The simple replacement of the oxygen snsor will not solve your vehicle's problem. Therefore, before replacing 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 miss 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 miss 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 fast contaminate the oxygen sensor Slower or miss sensor signal output. Sensor head shows red-brownish metal
Oxygen sensor contamination by hydrocarbon depots Faulty idle air control electrovavles or stepper motors, faulty pressure sensors or other engine management components cause a too rich mixture, which contaminates the oxygen sensor Slower or miss sensor signal output. Sensor head shows black hydrocarbon depots.
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 miss sensor signal output. Sensor head shows greasy oil depots.
Oxygen sensor signals modified by bad electrical connection Moisture or dirt into the sensor connector, as wll as poor or incorrect wiring connection of "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 shifted characteristic, or incorrect signal levels, or gives no signal output. Further damages may result to the sensor itself or even the vehicle electronic control unit.
overheated oxygen sensor defective ignition module, incorrect ignition timig, excessive spark advance, cause pre-ignition and engine knocking, with power loss. The exhaust has reaches a too high temperature and overheats the sensor. The sensor is damaged and gives no more signal outout. Overheat 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 inside ceramic 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 harmess can be noticed.

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