You can check the O2 with a DVM..basically if your car is like the 201's the connectors for the O2 are under the mat on the front passenger side. Just hook into the connection in parrellel using a small shunt inserted into one of the black connectors while leaving it connected (not the white ones as they are for the heater circuit) to which you attach the positive alligator clip...and then ground the black to frame(seat bolt or similar). With the motor warmed up, and held at about 2500 rpm's you should see the voltage fluctuate above and below .5V (Dvm set for 2v). If it is not functional, you will see a reading that stays below .5V.

If the condition you are seeing is similar to what I had, then your O2 may no longer be functional. They blind pretty quickly in a very rich air/fuel condition. At least mine ran well for a little while...so I knew the O2 was contributing to the problem...but the real cause was the failed ECU..creating the rich condition that was blinding the O2's.

We also had similar readings to yours at pin 3 when checking voltage with the eha disconnected and ignition on but motor not running before swapping ecu's...With the new ecu we got 11.9V, and then when running around 6.5 - 7 V once the air fuel mix was leaned back down (from memory..it was three years ago now). Now this was in a 16V, but I wager they are pretty similar readings for your car....dependant on the KE function.