So I have a 2002 trailblazer that had a blown engine so I swapped it for one from the junck yard. The engine from the junk yard was a 03 trailblazer. The point is that once I installed the engine and went to turn the key it cranked but no start . I checked the ground cables and fuses and relays and everything is good . I plugged in scanner and it gives me the code P1681 PCM internal performance. If some could point me in the right direction that would be greatly appreciated