2003 Dakota, P1604

I have a friend with a 2003 Dakota with about 100,000 miles on it. It recently failed inspection because the CEL was on, so I offered to scan it to see what was wrong.

The only code I present was a P1604, which means "Loss of IPC Serial Data". To the best of my knowledge, the only repair for this is to replace the whole PCM. Is there any other possible cause?

Thanks!