Can the PCM enter a closed loop if there is a faulty oxygen sensor? In reading my Haynes, it says that then the PCM won't enter closed loop if there is a problem with the oxygen sensor. I have P0155 and P0133. I hooked up a scanner to the car while it was running and the scanner showed the PCM to be in closed loop despite the SES still on.

 

P0133 is for slow response, Bank 1 pre-cat. The code can only set if the PCM is in closed loop. P0155 is for a faulty heater circuit on Bank 2 pre-cat. The sensor can still be functioning, it just may take longer to heat up.

The PCM just looks for O2 sensor activity, to indicate they are heated up and working. Once it sees the activity, it switches to closed loop. One of your sensors is moving slow, but its still "working", the other has a problem with the heater circuit, but apparently its getting hot enough to show the required activity and kick it into closed loop.