I am trying to tune the PIDs of my V6 Hotends but I am a little confused. First I run the autotune command via Repetier. Then I tansfer the new PID values via the M301 P.. I.. D.. command via repetier to the printer. If I check the parameter in the lcd-menue I find exact the transfered values there. But if a set the same values in configuration.h eg #define DEFAULT_Kp 5.0 #define DEFAULT_Ki 0.50 #define DEFAULT_Kd 50.0 save and load the firmware I always find following values in the lcd-menue: PID-P 29.20 PID-I 4.73 PID-C 45.33 independent of what I set in configuration .h I double checked if I edit the correct configuration.h and saved before compiling and uploading. I think I found the reason: Malrin RepRap Wiki: EEPROM If you have established known working PID constants, acceleration, and max-velocity settings for your own machine, you can set them, then store them in the EEPROM. On each boot-up, Marlin will automatically load these values from EEPROM, independent of what your compiled Configuration.h says.