The procedure is as follows:
power on the printer. You let it auto calibrate to see the ON-LINE message on the display.
press PAUSE to pause the printer
press RESTART and keep holding it for 4 seconds to go to the User Menu
the printer shows <1> RESET
press FEED (5x) to go to <6> AUTO CALIB
press PAUSE (1x) to enter AUTO CALIB
press FEED until you can see OFF
press PAUSE (1x) to go back to <6> AUTO CALIB
press RESTART (5x) to go to <1> RESET
press PAUSE (1x) to reboot the printer
The printer should start with Auto Calibration de-activated.