Err 05 with Canon 20D

I am having recurrent problems with my Canon 20D. I have 3 lenses (85mm f1.8, 75-300mm IS, 70-200mm IS). When I bought the 20D one year ago, I soon had problems with an error (I think it was Err 01); no autofocus, aperture reading was 00, and no photo). I sent it back to Canon 3 times before the problem was resolved. Now a year later, I get Err 05 when using the 75-300mm IS lens. When pressing the shutter half way, the shutter speed varies to adjust, but the aperture reading does not and reads 00, and no autofocus. So far, the 85mm lens is working OK. I am getting tired of sending this back to Canon. Any advice ?

I dont have my manual with me, but isn't a ERR05 a problem with the pop up flash?

Yes - pop-up flash. What mode is the camera in? Can you manually pop up the flash? Do you have a shoe-mount flash unit?

Sometimes the manuel pop up flash works, sometimes it does not. I was fiddling with this when the problem occurred. And the problem occurred in both manuel and auto modes. In auto mode, even after turning the camera on and off several times, after pressing the shutter, the shutter speed would adjust but the aperture value read 00 and did not adjust. The autofoucs did not work and no picture. It problem occurred with the zoom lens (75-300mm IS) and not the 85mm f1.8. The camera seems to be working now so I will and see before sending it back to Canon again. Thanks for your help

If your aperture reading is 00 it is possible that the camera is not making contact with the lens. Try cleaning the contacts on the camera and the lens. I don't know if this will work, but it won't hurt.

ScottE wrote in post #2368109
If your aperture reading is 00 it is possible that the camera is not making contact with the lens. Try cleaning the contacts on the camera and the lens. I don't know if this will work, but it won't hurt.

If that were to happen though, your going to get the infamous ERR99

If the flash isn't popping up reliably either automatically or when manually deployed, the release and pivot mechanisms may be a bit grungy. Try exercising it; swinging it up and down several times. Also check on the hot shoe - under one of the rails is a microswitch that signals when there's a flash in the shoe. If this is stuck down the pop-up flash won't.

Jon wrote in post #2372380
...Also check on the hot shoe - under one of the rails is a microswitch that signals when there's a flash in the shoe. If this is stuck down the pop-up flash won't.

Oh yea, I found out about that one the hard way. I got a hot shoe protector from another camera and plugged it in. Later, when trying to use the pop up flash I wouldn't pop up. It wasn't until I removed the little plastic protector that it went away. I wasn't getting the ERR05 though.