With power on, engine off, I'm getting 5v on the gray wire, and .5 volts on the return wire. Either you have another bad pcm, or low voltage between the PCM and the battery. If you have a scantool that can tell you the PCM voltage, that will get rid of the low voltage test.
Other than that, I cannot think of anything else. But, don't run off yet. I need to renew my AllData subscription for the Blazer. I'll research more once I do that.