Lambda sensors

Causes and Effects of Oxygen Sensor FailureCauses and Effects of Oxygen Sensor Failure | A 19Whilst there are many factors that will contribute toaccelerated oxygen sensor failure, it should beremembered that an oxygen sensor is a wearing part witha specific service life not unlike a platinum spark plug.The oxygen sensor should have a service life ranging from50,000 Km - 160,000 Km dependant on sensor design,however this can be dramatically reduced by variousconditions including overheating of the sensor, chemicalpoisoning and impact damage.Excluding physical damage, the majority of theseconditions will result in the failure of the ceramic thimbleby affecting its porous nature. This will result in a sensorthat is slow to react to mixture change as shown below. Aslow sensor will tend to make the air / fuel ratio of thevehicle drift rich.Sensor Voltage OutputNormal Sensor - Voltage “cycles” between 100 & 900 mV.The average output from the oxygen sensor will be ~450mV.Important Facts About Oxygen Sensors Oxygen sensor life spans will vary between vehicle andsensor designs, and are effected by many factorsincluding fuel quality and vehicle operationalcharacteristics. Oxygen sensors should be checked and/or replaced at -50,000 km for single and two wire sensors.80,000 km for three or four wire heated sensors.160,000 km for planar type sensors Oxygen sensors can be contaminated in many waysincluding -Lead fouling from incorrect fuel.Severe carbon/oil fouling from engine/emission controldefects.Contamination from silicon products. Thermal stress damage (fracturing of the ceramicthimble) from excessive water in the exhaust, ie- blownhead gasket. Contamination of the oxygen sensor basically results inthe coating of the platinum electrodes and thereforeinsulates them.**NOTE** - oxygen sensors cannot be cleaned!! Oxygen sensors will die of “old age”, they are awearing service part like a platinum spark plug. As the oxygen sensor deteriorates over time, or iscontaminated, the output from the sensor slows down.This causes the average that the fuel managementsystem calculates to reduce. The lower average gives the impression that the engineis lean and the fuel management systemovercompensates to rich.Slow, Contaminated or “Tired” SensorVoltage slowly builds up and then rapidly drops off. Theeffect is that the average will drop causing a richcondition. Due to the fact that the engine will operate in a richcondition at all times, fuel consumption is naturallyhigher.2009 | 2010 Bosch Automotive Aftermarket