P0420 and P0430

[stephenxchen]

hi guys, please help

I am in California, just bought a used 2010 BMW x5 with about 95,000 miles on it. I was being cautious, and asked previous owner to provide a smog test, which she did. so we made the deal, paid her, drove home.

next day, 2 codes showed up on my Acron CP9580 scanner: P0420 & P0430

can someone please help me decipher these codes, and tell me WHAT needs to be tested/replaced:

at idle:

CAT Temp11: 802
CAT Temp21: 795
Long Term Fuel Trim 1: 5.5
Long Term Fuel Trim 2: 7.8
Short Term Fuel Trim 1: -0.8
Short Term Fuel Trim 2: -0.8
O2S12(V): 0.705
O2S21(V): 0.685

at 30mph:

CAT Temp11: 1131
CAT Temp21: 1140
Long Term Fuel Trim 1: -0.8
Long Term Fuel Trim 2: 0.0
Short Term Fuel Trim 1: -3.9
Short Term Fuel Trim 2: -2.3
O2S12(V): 0.690
O2S21(V): 0.470

[peter2772000]

PO430 is related to cat converter efficiency being below threshold.
From what I've read (have the same code on my FJ Cruiser), changing the O2 sensors may get rid of the code for a while, but most probably the cat(s) is on its last legs.