تلوث سيليكوني من مادة مانعة خاطئة

Silicone from the wrong sealant poisoning an oxygen sensor. Ordinary silicone sealants release compounds as they cure that coat a sensor's element permanently — which is why sensor-safe sealant exists and why the distinction is printed on the tube.

The failure is fast and total. A sensor exposed to curing silicone can be dead within a tank of fuel, so the timing is unmistakable: a sensor failing days after an engine was resealed. A white powdery deposit on the element confirms it. The important half is that a replacement sensor is destroyed the same way if the sealant is still curing, so the joint must be redone with the correct product rather than merely fitting a new sensor.