This TSB was released by General Motors, covering most of their large SUV’s and vans that have been produced from 2002 and up. The related DTCs that a technician may find are P0420, Catalyst Efficiency Below Threshold, and/or P0430, which is the same thing, Catalyst Efficiency Below Threshold, just for bank 2. Technicians are seeing these codes on low mileage vehicles, or vehicles that have recently had the catalytic converter replaced.
On new vehicles, DTCs P0420 and P0430 are disabled for the first hour of run time, to allow for break-in of the catalytic converter.
So, if these codes are found on a new or low mileage vehicle, the technician should verify engine run time. If it is less than one hour, it is possible that the battery was disconnected at some point, or something else caused a power loss during manufacturing.
If this happens, it may allow the catalyst efficiency diagnosis to run before an hour of engine run time has been achieved.
The reason is that the converter may not have completed a thorough break-in cycle, which can cause these codes to falsely set.