service mode For HP Laserjet 8000 8100 and 8150 Series

1. Hold down SELECT and JOB CANCEL while powering on the printer, until all lights are illuminated and the Display is blank. (If the Display Panel reads INTERNAL TEST at this point, the keys were released too soon. Repeat this step until successful.)
2. Press MENU, then SELECT. The message SERVICE MODE is displayed briefly, then the printer automatically begins an INTERNAL TEST. After several seconds, both Control Panel Indicators turn off. (The printer may display WARMING UP if it has not warmed up completely.) After the printer has warmed up and passed the self test, SERVICE MODE is displayed.
3. Press MENU once to display SERVICE MENU.
4. Once it says SERVICE MENU press ITEM to scroll through service mode items.
To exit the Service Mode press GO.