Mooseman, I understand what you are saying, and I admit that you are far more capable of a mechanic than I. However, I have learned that GM does not always include all valid DTC codes for their vehicles in their factory service manuals (FSM). About 5 years ago I got a P0466 on our 99 Silverado with a 5.3 l engine. I could not find P0466 in my FSM for the Silverado, it was not on Alldatadiy.com, etc.
When I searched for it on Google, Google kept trying to change it to a P0446 code. Well, I finally found an obscure listing for a P0466 code and it led me to check out the fuel tank pressure sensor circuit. Low and behold, the fuel tank pressure sensor had died. I replaced it and no more P0466 code.
Also, I do agree with you that P0445 does not show up in my FSM for my '04 TrailBlazer. Now whether or not that means it can't throw a P0455 code, I do not know, but I would not be surprised if it did.
Regards!