20 Most Recent Canon EF-S 17-85MM F/4-5.6 IS USM Lens Questions & Answers

This is more than likely an broken ribbon cable problem. This cable in the lens flexes each time the lens zooms in and out and eventually after a long period of use it will break. If the lens will focus manually but not auto focus this is a pointer to that problem. It means a trip to the repair shop but check out the repair cost first as you may be able to purchase a second hand lens for about the same money.

clean both the lens's contact and body's, if corrosion use nice emery paper.

That should be send back to Canon for repair.

Hi all,

I've had the same problem. So I decided to give it a try because I didn't find any solutions on the net. Unfortunately you have to pay pretty much for a Canon lens while the internal quality is pretty cheap, the whole mechanism is of plastic and this is also the problem. And after a while some screws will vibrate loose from the plastic components and canon could have done this better.

Probably within your lens is now one of the three zoom mechanism screws complete removed and you will notice that there is some abnormal movement in the zoom part. Unfortunately these screws are deeply mounted inside the lens and you need a lots of skill and patience to get it fixed.

First you need to completely disassemble the lens, and please make a picture of your lens after every step you make because I had to disassemble my lens 4 times! Because some of the elements was not right in place.

I will try to place a more complete description later today including some pictures.

Regards Gert

• communication between the lens and camera body is not funcitoning properly
• remove the lens clean the lense contacts
• if problem still persist turn off the autofocus switch . you might have a defective flex cable it must be replaced

Needs New Aperture Flex.

If you got what some call "pumping" or "hunting" focusing, the lens tries to focus but seem to be unable and ends with a clearly unfocused image. Then your lens is dirty inside. You can fix it yourself - BUT...DONT DO IT, IF YOU HAVE TEN THUMBS, If you break it - i warned you right here - i am not to blame - DONT DO IT!Well, its kind of hard to describe, but i will try anyway. If you have disassembled your lens so much that you have the usm part as a separate unit, then try an have a look inside the usm tube to see what happens when you manually change the focus.Inside the tube there is a small slit where the optical sensor is hidden, you can\'t get to it without removing the rear part of the usm unit. This is tricky, because one of the flat cables is taped to the inside of the tube. You\'ll have to gently remove this cable from the tube - WARNING: these cables are very sensitive to pulling, they will break if you pull it too hard. (This is probably why Canon Service Centers are replacing the complete USM unit, instead of trying to repair the darn thing)After the rear part has been removed, you should be able to see the plastic/glass sensor plate about a 1/4 of the diameter of the tube.DON\'T touch this plastic/glass thing with anything hard, use a fine (new) paint brush to clean it. If you have a magnifier about 5x to 8x, you should be able to see that the sensorplate is dirty.Try to move the sensor itself (not the plate) by manually focussing, so that you can clean the plate beneath it.put the lens back together, it worked wonderfully with my lens. Will it work with yours? don\'t know.And as always, you are on your own, if you break it - your problem, not mine!CheersPer

Sounds like while you were fixing it, you crossed a thread somewhere. For the focus to be out on both manual and auto is a give in. All it takes is the finest spec of sand or... bogey to get wrapped up in the threads...and it's night nurse. You can try putting it in Manual Focus Mode, rotating the lens slowly till you hear or feel resistence...then you'll get a better idea of where you're at. If there's resistance, it's crossed - if there's a gritty sound, a piece of sand or snot is throwing out the barrels.

Good luck. EF-s systems are a bit trickier to put BACK TOGETHER. Taking apart is the easy part! :)

What is the error message? Usually, it is because the contacts have eroded away, or not the correct lens for the camera type. If it's 999 .. usually that is contact error.. cleaning can help.. both at camera and lens. If it's ERR, sometimes, it is the Card... which runs the entire camera. check to see if it's card and go on line to see if there is a new firmware update for you make and model.