Where are you located?  Does your 4Runner have a 4 cylinder or V6 engine?

The catalyst is monitored by the #2 O2 sensor circuit, which uses 2-trip
detection logic.  After clearing trouble codes, the electronic control
module (ECM) has to see 2 consecutive trips without any faults from any
sensors to be in "ready" mode.  There are specific parameters, like a
certain road speed, distance traveled, transmission gears used, coolant
temperature, O2 sensors warmed up, etc. that must be met for a drive cycle
to be counted by the ECM as a "trip."

The information is listed in Toyota TSB EG003-02 "Readiness Monitor Drive
Patterns (Revised).
Here is a link to a site with the TSB:
http://autocenter.weber.edu/OBD-CH/documents/newdocuments/toyota/TSB_EG003-02_(r
evised).pdf

Follow the drive pattern on Page 12 if your 4 Runner is a U.S. 49 state
model or P. 13 if it has CA emissions.