Old extruder line. CPU 315-2 DP, five ET 200M slaves on PROFIBUS, 1.5 Mbit. Slave 5 is in an outdoor panel by the silo.
Every time that panel loses 24V, which is a few times a week now it's cold, the whole CPU goes to STOP. SF on, DP LED red. Buffer top entries, near enough as written:
"STOP caused by rack failure OB not loaded (OB 86)"
"Distributed I/O: station failure, station 5"
We put a new DP cable on slave 5, checked the terminators and swapped the IM 153 with the one on slave 4, and it's the same every time the panel drops. Losing a whole line for one outdoor slave, and I'm out of ideas. Is it the CPU firmware? It's an old one. Or is there something in the CPU that decides a missing slave should stop the lot, I think there must be.
It's not the cable and not the firmware. The buffer already told you: OB86 isn't in the CPU. Which STEP 7 version, and have you got the project? Look in the Blocks folder for OB86.
STEP 7 5.5. I've got the project. Blocks folder has OB1, OB35, a pile of FCs and DBs. No OB86. No OB82 either, and I think that's the whole story.