Help, P1154????
Other times it is due to Silica from RTV silicon gasket materials. The sand like particles from the RTV embed in the molecules of the O2 sensor element and plug up the surface. This results in a lazy O2 response. The sensor will have a whitish appearance if this is the case. Silica contamination can also come from fuel. Some companies use silicone to raise the octane rating. It can also come from lubricants used to install hoses and fittings. Leaded gas will also contaminate your O2s. This lead glazes them and is difficult to detect visually.
Oil deposits will also contaminate your O2s. The sensor will have a dark brown appearance.
Additives like Ethylene Glycol will also cause this. This also gives the O2 sensor a whitish appearance.
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