Cause
Silicone contamination from incorrect sealant
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.
Typically an easy fix. Often worth checking before paying anyone to look.
Codes this can cause (1)
Codes where this is a likely explanation first, rather than merely a possible one.
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