pending trouble code

lately i have been getting a pending trouble code, PO136, for my 2001 2.7L. The ultra guage tells me i get the pending trouble code only when im in stop and go traffic, not at any other time. it may happen once a week r once every 2 weeks. I just clear the code but is this something that needs to be looked into since its only pending? Also, i do not get a CEL and im still getting good MPG. sometimes the truck will idle a little low (650-625rpm)when the A/C isnt running so i dont know if this has anything to do with it but it has been idling like that ever since i canremember and i never has this code pop up

*also, the truck doesnt have the rear Cat but i do have the URD sensor simulator and it has never given me problems

 

P0136 02 Sensor Circuit Malfunction (Bank I Sensor 2)

Bet it has everything to do with removing that rear cat as this refers to the O2 sensor furthest removed from the engine. I would guess it's probably not anything to worry about unless you have emissions down in Louisiana.