ABB AC800M (PM861) error redundancy

I am a maintenance engineer in a sugar factory, I have no experience with ABB equipment.
The factory uses ABB's DCS system 800XA V5.1 and Control Bulder AC800M software. I have two redundancy PM861 controllers together, the Upper controller has an additional CI853 module.
The peculiarity of my factory is that it only works for 4 months/year, After the operation period, the whole control system will be powered off and the PLC system will lose all data. Next year, we will re-download the program to PM861 to work again.
This year, after downloading, the system does not receive redundancy, the Dual Led light flashes on the upper controller for a while and then turns off. I have tried to check the cables connecting the upper and lower controller and they are normal. The controllers can all work individually, it's just that they don't redundancy with each other, and when they work together, it's likely that the backup controller will fail and be deleted. I have tried unplugging the battery, downloading to both PLCs separately and then restarting, but it still doesn't work.
I have one license Usb, when I downloaded, I didn't put usb into Workstation. Does it affect the redundancy error?

What would I have to do to test in this case. I attached some picture about this case.
Thanks everyone.


Hi Troung,

I Think you can reset this by (very) carefully press "INIT"-button for 5 sec. on the Controller with Failure (F) LED. You will the running (R) LED flashing, this means reset is done, so wait till the DUAL LED turn on. PM861 sometime fails after power on.

Next time, try to keep the battery on power, so it will keep your application. Then power on the upper CPU (wait 3min), then the lower CPU.

That's all.

When still problem, then others steps need to be taken.

Best regards,

Long (800xASolution at