FAQ: DIAGNOSING A WATER DAMAGED LAMBDA SENSOR
Lambda sensors are intolerant to thermal shock. Immediate destruction will result if the sensor tip is exposed to water or liquid fuel (especially alcohol) while the sensor is powered and/or hot. Sensor failure is a common occurrence when the sensor is installed into an exhaust system tail pipe, and power is applied to the meter before the exhaust system is fully warm and condensate free.
When hit by a liquid the sensor's ceramic element is usually shattered. Sensors with this damage, cause a 'SENSOR FAULTY' message to be repeatedly displayed once the meter judges the sensor to be fully warmed.
This condition can usually be confirmed be shaking the cooled sensor while holding it in such a manner to prevent the sealing washer rattling. In a quiet environment a rattle will be heard from the shattered sensor element.