I've got a PO172 Code, "system too rich, bank no. 1"

I'm taking it in tomorrow but want to get an idea of what might be the problem before hand. I believe this means the first passenger side 02 sensor (bank 1, sensor 1) is detecting too rich a mixture.

Is this most likely a faulty 02 sensor, or something else? It seems like misfires would cause a lean situation, not a rich one, and I can tell from my scan tool that I haven't had any misfires on my 8 cylinders....

Any comments appreciated....I'm curious as to why the Code doesn't specify which sensor (row 1 or 2) is getting the rich reading, but I guess it's a no-brainer that the one after the cat couldn't be exposed to such scenario?!!??

 

p0172 is a rich code for the ho2s-11. thats the first o2 not the cat monitor. good luck on your repair.