Originally posted by 1stGenCRXer
The CEL code won't show a heated o2 fault if the car doesn't have a heated o2 
The o2 sensor doesn't measure pressure at all, nor does it make any fuel adjustments based on pressure. That is the MAP sensor's job. He's in california, aka, not allowable. Then again, having no cat is a no-no as well...
The O2 sensor, is essentially a pressure sensor. It senses the pressure of the unburnt oxygen, yes.
I thought only the wideband units were heated, maybe the 4-wire, in his car is also... dunno.
-PHiZ