I've been working on a 2005 Chevy Silverado with a 4.8L and an Ls1b pcm. When I try to read the stock tune from the pcm it recognizes the controller but fails to unlock it and read the tune even when i try the alternate unlock strategies. I was able to read the DTC's and it threw a b1000 ecm malfunction code. I'm wondering if there's something i'm missing or if the pcm isn't any good. Any advice would be appreciated.