Help code P0153, but I get no readings from any of the o2...

My brother in-laws '97 Explorer sport with the v6 (ohv) 130k miles - has a code P0446 = Evap emission control system vent control circuit malfuction - after checking around I read the the most common cause is a bad Purge silonoid above the spare tire, which I quess is what I'm going to replace...

but my main problem is the code P0153 = 02 sensor circuit slow response bank 2 sensor1

I have any Autoxray 4000 and when I monitor his explorer I get 0 readings on all (3) of his 02 sensors!!!! so just to make sure it was the scanner I hooked it to my '97 Explorer 5.0 and I get voltage readinges from all (4) sensors....

so I rest his code and scanned it again yesterday and the same (2) codes are back.... my thing is if I'm not getting any readings from his (3) o2 sensors, shouldn't there be more codes for it, instead of just the slow reponse from bank 2 sensor 1? I mean I should be getting one for the other side since it must not be working... I'm just confuse... I want to make sure it couldn't be something else before I go out and have him buy all (3) o2 sensors....