Mitsubishi MELSEC-Q series Programming Manual page 246

Auto tuning procedure
Start
Since the PID constants are overwritten at completion of auto tuning,
record the PID constants as required.
Set the loop tag and operation constants necessary for auto tuning.
Change the operation mode (MODE) of the tuning target loop to Manual (MAN).
Make sure that the process of the tuning target is stable.
(Adjust the MV so that the process is stabilized as required.)
Disconnect the S.2PID/S.PID instruction of the tuning target loop and connect
the S.AT1 instruction to where the S.2PID/S.PID instruction was located.
Turn the auto tuning start signal (e1) to Start (1).
(Auto tuning in execution)
Auto Tuning Completed (BB16) turns to Completed (1) at end of auto tuning.
Turn the auto tuning start signal (e1) to End (0).
(Auto Tuning Completed (BB16) turns to Not completed (0).)
Check the PID constants stored in the loop tag.
Disconnect the S.AT1 instruction of the tuning target loop and connect
the S.2PID/S.PID instruction to where the S.AT1 instruction was located.
Make fine adjustment during normal operation.
End
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