Does the oxygen sensor rely on a good ground from the sensor body to the rest of vehicle ground? I wonder if it would make sense to put a ground strap from the header to the block, since the gaskets might be electrically insulating?

I have a 3-wire heated sensor, but as I understand it, the power/ground is only for the heater. The sensor ground is still through the exhaust system itself.

 

The gaskets might be insulating, but the bolts aren't.

 

Yeah, it struck me after I posted.

But then why do OEM's sometimes put ground straps on their exhaust systems?

 

I don't know... redundancy, corrosion resistance...