To test the displays on the key panel:
1. Enter the service mode.
2. Simultaneously press Stop Belt, Grade Up and Grade Down.
3. The display cycles through one digit at a time in each display, starting from left to right across the panel. Each digit displays the number 8 and the associated decimal point for one second, then turns off as the next one lights up.
4. When this is completed, the LEDs light up individually, starting from the top. The Select LEDs illuminate first, followed by the Units LEDs.
5. After the LEDs are tested, all the digits in all three displays simultaneously count up from 0 through 9.(No decimal points light during this count.)