Dan, I'm thinking he has a bad circuit in the ECM and needs to replace it, but also needs to find out which device on circuit #1 could have failed and caused the issue with the PCM. If he doesn't correct the issue with the device, the same thing could happen to a new PCM. Do you have any experience with this type of thing? If not, is there someone else we should pull into this.
If I'm out in left field let me know, I am just trying to get some direction on the problem he is having.
2001 Bonneville SSEi (retired at 365,000 Kms.)
2014 Jeep Grand Cherokee Overland (yes, I know its not a GM)