My auto focus not working I have cleaned connectors

First of all you need to clean the connectors on both the lens and the camera. Do this by using a pencil eraser being careful not to get bits in the camera or lens. If this doesn't clear the problem is it that auto focus doesn't function with any lens. If that is so then you need a camera repair. If auto focus is only non functional on the Sigma 170-500mm and you can manual focus then the probable problem may be a broken ribbon cable in the lens itself. This will need to be replaced. Usually a quick and relatively cheap job.

It may be that the ribbon connector has broken in the lens.

If it focuses manually and not in auto focus the probable problem is a broken ribbon cable connector in the lens

Are you using an auto-focus m4/3 lens? I have about 20 lenses for this camera and only 1 of them is an auto-focus m4/3 lens. I have an adapter so I can use my 4/3 lenses on it in auto-focus mode along with other various mounts (including cctv) that do not support auto-focus. So if you are using a non-auto-focus lens, you will need to manually focus the pictures.
If you are certain it is an auto-focus lens, are you sure you have it set to auto-focus?
What settings do you have your camera set to (aperature mostly is what I'd like to know)? Try adjusting your aperature to be small (to increase your DOF).
Also what lens are you using and what is your focal distance? It could be your lens has a larger or shallower focal distance than what you are trying to achieve (like a macro lens doesn't work that great for landscape photography or a telephoto lens doesn't work great for macro photography).
Last thought: is your lens or sensor dirty? A dirty lens can cause focusing issues if it is REALLY dirty and a dirty sensor can too (sensor is a bigger pain to clean. I strongly recommend taking it to the pros as they scratch really easily). Dirty lenses can be cleaned with a blower and a lint free cloth and rubbing alcohol if those 2 things don't clear it out.

Happened to me once too. It was due to humidity. I had to take out my lens and clean the metal connectors on the lens and body carefully. If that doesn't work you lens auto focus mechanism may be faulty.

So you having problem with AF problem?

Try this (mind your camera to protect it from dust OR another small parts to get in while you opening):
1. Re-connect the lens and the camera.
2. Make sure the connectors is clean.
3. Connect it together again.

Hope this will help! Any questions? Feel free to PM me =]

I had the same issue with my Nikon d60...my 18-55mm did auto focus but my 55-200mm only manual focused, i thought it might have been my camera as i heard that not all lenses are compatible with my d60 but it turned out to be the focussing motor or something that was damaged, it was making a very funny noise when it tried to auto focus with it,like a screeching sound..if this is the case you should get it repaired and looked at, also check on the lens if it says it is a AF lens,if so make sure th switch on the side of the lens is switched on AF not MF. hope it helps

cheers

google its user manual

changing lens from stock might be the issue
or 8 years auto focus sensor may be stuffed

Hi    The switch is held on by two screws you can remove the screws    and the switch will fall off it will need cleaning 

the plug for the red wire, or the 3 wire connector? with the red wire, a simple crimp on connector from your auto parts store should take care of that... the other plug, I donno if your auto parts store would sell that or not, you may have to check a parts yard.... if you're talking about on the alternator itself, well, that's gunna be much more difficult, I don't really think it could be explained here, BUT, an alternator from a parts yard around here only costs $15-$30... (of course, getting it in and out of a Focus is a bit of work.. buuuuutttt....)