Service VME - DTC P0420 or P0430 - keywords catalytic converter oxygen sensor

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

This message concerns 2004-2006 Cadillac CTS, SRX, STS, XLR and Buick LaCrosse and Rendezvous with LY7 3.6L and LP1 2.8L V6 or LH2 4.6L V8 engines. When diagnosing concerns with oxygen sensors, the following points should be followed:

1. Malfunctioning oxygen sensors will set a sensor related diagnostic trouble code. Do not replace the oxygen sensor unless diagnosis following the appropriate document in SI indicates that the oxygen sensor should be replaced. For example, the oxygen sensor should not be replaced if diagnostic trouble codes P0420 or P0430 for catalyst efficiency are present alone
2. When replacing the catalytic converter, do not replace the oxygen sensor. Transfer the oxygen sensor from the old converter to the new converter.
3. Oxygen sensors that are damaged due to underbody impact are not covered under the new vehicle warranty.
4. Please DO NOT cut the wires of the oxygen sensor when replacing it. x#

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.