To access service mode,
Turn off the printer, hold down the Center, right and bottom buttons all at once, turn on printer and keep holding the buttons down until you see the LCD display the cartridges. Let the printer come all the way up. Your LCD menu will look a bit different.
You have a lot more control over cleaning in Service mode. 4 levels of pairs cleaning, unlike the cleaning accessed from the computer. You can also switch from Matte to Photo and back in SM without wasting as much ink. The printer will not run a cleaning cycle.
I would recommend doing a quick search on this site before you work in Service mode as there are settings in there that can be altered by mistake and can cause problems. I am away from my printer or I would give you the steps to get to the cleaning. I am sure it's in this forum somewhere however.
To get out of SM, turn off the printer, (I wait about 10 seconds after turning it off), then power back on.
Note, you can run in SM with no problems all the time, however you can't do a nozzle check from the printer in SM and you can't set a paper type. Still prints fine. When I am working with a lot of matte and photo ink jobs, I tend to stay in SM since the swapping is so much faster and takes less ink.