PID Loop... stopped working

[Davo 0]

Hello again. We have a 224xp with a profibus module. The program seemed to be running well, with a PID loop to govern drive output. While troubleshooting the logic for alternating the drives, the PID just seems to have stopped working. This is my first time messing with a PID, and the shop guru is in the field today. Is there some common error I should be looking for? Is there an online primer anyone recommends? I haven't been trained on this yet.

[Davo 0]

Apparently the issue was some logic prior to the PID Loop in the same network. O.o