EOS 90D autofocus keeps switching from AI to M

[Birder_Girl4]

I've been using the EOS 90D for three years with no issues.  I use AI focusing mode as it best meets my needs for bird and wildlife photography.  Recently the focus mode has begun jumping from AI to M with just the slightest move of the camera.  I set it to AI and as soon as I press the shutter it jumps back to M. This has been happening with every lens I've tried and with various exposure settings.  The battery is new and fully charged, and all camera and lens settings are at AF.  Any idea what is causing this?

[deebatman316]

All of your lenses work on a different camera you mentioned but not the EOS 90D.

[Birder_Girl4]

Sorry, I just checked, and it is Error 01.

[deebatman316]

Is this on the 90D? What I would do is retest every lens and set the aperture to something small like F/8. Smaller than the maximum apertures of all lenses. Since these are all variable aperture lenses. Then press the depth of field preview button. This will make the aperture stop down. Canon focuses wide open until the exposure is made. The test can easily be done with the camera set to Av Mode.

[Birder_Girl4]

Yes, this was on the 90D.  I just tried your latest suggestion with each of the above-mentioned lenses, switched to AV mode and tried to set the aperture, but in each case I got a message "Cannot adjust Aperture because no lens is attached."  I'm beginning to think that my 90D is dead, or is there still some hope for a fix?

[deebatman316]

Does the camera report F/-- or F/00 in the viewfinder, top LCD screen and rear LCD screen. Or does it show an actual F/ Stop value such as F/5.6 for instance.

[Birder_Girl4]

F00

[deebatman316]

Are all of these lenses working with your EOS 7D classic. If they are the problem has to be with the camera body.

[Birder_Girl4 · Accepted solution]

Thank you for your suggestions.  I contacted a local repair shop, if they can't repair the 90D they will ship it to Canon for me.  

[408_Birding]

Hi I just experienced the same issue with my setup today. They are almost identical to yours.

Canon 90D + Canon 100-400mm 4.5-5.6 ISII USM

I was using back-button AF to focus in on a subject and viewing through the viewfinder when the scene started jumping around. Often with a loud "clunk" sound.

I took it to a local camera shop to have them test both the body and lens and the lens seemed to work fine when paired with other bodies they used. So it seems like my issue is the same as yours - with the 90D itself.

I also got this error:
Err 01 - Communications between the camera and lens is faulty. Clean the lens contacts. 

I cleaned the gold sensors on the lens with a dry cloth but no dice. 

Wondering what you found out from Canon or your repair shop and hope to hear how it was fixed!

Thanks