Why does my Nikon D750 show an fEE error with some D-type lenses that work on another Nikon body?

Question

My Nikon D750 now shows an fEE error with two lenses that previously worked on it: an AF-S 17-35mm f/2.8D and an AF 80-200mm f/2.8D. Both lenses still work on my older Nikon D100, and another lens, an AF Micro 60mm f/2.8D, works normally on both bodies.

I’ve cleaned the lens contacts and locked the aperture rings at the minimum aperture as required, but the D750 still reports fEE with those two lenses. If I change the D750 setting to use the aperture ring, the error goes away, but the aperture stays stuck at f/22 and turning the ring has no effect.

Does this point to a problem with the D750 body rather than the lenses? If so, what part is most likely at fault?

user11924 · Accepted Answer

It's possible your D750 is physically damaged. It sounds like the Ai (aperture indexing) sensor is having problems.

Prior to your D lenses returning fEE errors, did you perhaps try to mount an older, non-Ai lens to your camera body? If you did that, you could have bent or damaged the Ai index tab or the Ai sensor.

First, check if the Ai index tab moves. With the lens off the body, locate the sensor tab as shown in the image below. You should be able to rotate it easily with your finger. It should go from the ~1:30 position (upper right) to about the 10:30 (upper left) position.

^{Location of Ai index lever on Nikon D750 body (circled in red)}

If it moves easily, then I would suspect the sensor that the lever connects to. Although the thread, 'D610 "fEE" error, camera or lens??' at nikonrumors.com, originated with a problematic D610, a later poster had a similar problem on their D750. Their problem was diagnosed as a faulty "Aperture F-FO Base Plate Unit":

I had the same issue on my Nikon D750. I checked the contacts, made sure that lenses (as I had this with more than one lens) is locked on highest aperture. I even changed the mode from command to focus ring (helped a bit, but I did not have full functionality).

So I took it to Nikon to be fixed.

There is a small ceramic part inside that is called "Aperture F-FO Base Plate Unit". It is fragile and easy to break. It can break from normal use, possible vibration going over speed bumps or if you knock your camera. In my case Nikon fixed it for me under warranty free of charge.

If they diagnose it as mechanical damage, they might refuse though - in such case (or if camera is out of warranty) you may purchase the part on ebay (make sure you purchase right part) and take it to local camera shop to be fixed.

The poster even linked to a YouTube video that shows how to remove and replace that part.

Why does my Nikon D750 show an fEE error with some D-type lenses that work on another Nikon body?

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