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?

[Birder_Girl4]

I originally posted about a problem with my 90D switching from AI focusing to M focusing.  Here is more information to clarify the problem.  I am a bird and wildlife photographer and use AI Servo for my photography.  Recently the focusing mode has begun switching to MF manual mode despite the fact that my camera and lenses are set to AF auto focus.  This happens regardless of which focusing mode (AI Servo, AI Focus, or One Shot) I try.  It also happens with each shooting mode I try.  This morning when I tried to shoot in AI Servo it immediately defaulted to MF manual focus.  I am now unable to get it out of MF, it appears to be stuck in that mode.  I did try to manually focus an image but when I pressed the shutter nothing happened. The problem began over a month ago but has gotten increasingly worse making it nearly impossible to use the camera.  I have no idea why this is happening and any help would be greatly appreciated  Is it time to ship the camera off to Canon for repairs? 

Thanks for any advice you can give.

_Birder_Girl4

[deebatman316]

What lens are you using please provide the FULL NAME of the lens in question. Not just for instance "EF-S 18-55mm" there are many variants of that lens. So the specific name is very important.

[Birder_Girl4]

Thanks for your reply.  I use the Tamron SP 150-600mm F/5-6.3 Di VC USD AO11 and the Canon EF 100-400 mm f4.5-5.6L IS USM.

I've been using both of these lenses with the 90D for three years with no issues until recently

Birder_Girl 4

[deebatman316]

I want to confirm the EF lens is this the original EF 100-400mm lens with the push pull zoom. Or the newer one with a dedicated zoom ring. I would try retesting both lenses on a different camera to see if both lenses are doing the same thing. Also the EF 100-400mm lens has mechanical focus override while in AF mode. You don't need to half press the shutter button to allow focus override to work. This lens doesn't have an electronic focus ring like STM, Nano USM and some early Ring Type USM lenses do.

[Birder_Girl4]

The EF100-400mm lens is the original with the push pull zoom.  The Tamron 150-600mm lens is 1st generation.  Both of these lenses work perfectly on my old 7D (first generation, not 7DII).

[deebatman316]

Do you have another lens to test out on the 90D to see if it still happens.

[Birder_Girl4]

I tried the EF 70-200mm 1:4L IS USM and the EF 70-300mm 1:4-5.6 IS USM.  The same problem occurred with both lenses on the 90D.  When I tried the 70-300mm lens "Error Message 3 Communication between camera and lens is faulty" appeared.

[deebatman316]

What Canon has listed for error 3 doesn't match what you have. Link to Canon USA This sounds like an issue with the body.

[Birder_Girl4]

I think this should read Error Code 30, not Error Code 3.  It says communication between camera and lens is faulty.