I have a 1997 3500 with the 6.5 diesel engine. Driving down the road the other day, the engine stalled. I attempted to crank it while it was moving and it eventually started back up. The service engine soon light came on and stayed on. I connected my code reader to it and got a P1621 code with another P1621 pending.

I've looked all over for what the P1621 means and what to do with it. Looks like a eprom write or long term memory. Does this mean replacing the PCM or what needs to get fixed?

Hmmm...thats a strange one. I've never encountered it before, and I can't see how it can mean anything other than a problem inside the PCM. Can you clear it?

I cleared it a week ago and it's back. I can't clear the pending one, and both are the same code.