'Err 01' on Canon 24-70mm f/4 L IS USM :( 

Thank you very much for the video. I have the same error on my Canon EF 24-70mm f2.8 MKI, but maybe some of my observations might be helpful for this model too for people who can't fix it immediately or don't know what the problem is. It might be the aperture connection cable which is damaged. If you hear some clicking when turning the zoom, then it is probably so. These connectors get stretched over time with zooming and then bend, get stuck, wear or get pinched and break. Another test is to see if your camera takes photos in f2.8 (or your cameras lowest f. value, i will write this now with the lowest F-Stop for my lens, which is f2.8, so convert it to your lens values if needed). Be careful to watch the front of your lens to make sure if your aperture is fully open. (You can play with the aperture settings in the camera and the aperture test button on the side of your camera. The aperture needs to be fully open). If the camera takes photos that way and AF works (If you put it in f2.8 mode and the AF doesn't work, check if the aperture physically really is fully open, at least on my lens that is the only position AF works) If that is the case for you the Aperture connector is most probably broken, which is a 10$ piece, however needs full disassembly of the lens and possibly soldering. Therefore I found some workarounds I want to share: In f2.8 the lens should always work with AF, I saw many other discussions which stated that also. I also can trick the camera into using different apertures by selecting a high aperture in the camera, e.g f8 and pressing the aperture test button multiple times until the aperture closes. Possibly also by pressing the shutter and getting the error message, but this is slower. It is not reliable, you can't be sure which aperture gets selected, as the aperture closes or opens a random amount. Look at the front of the lens for the aperture closing. In theory f.4 should be the aperture half closed, f.5.6 3/4 closed etc. I am not sure in what increments the aperture jumps, might only be full F-stops or finer or totally random and even enable normally not possible aperture values. Only thing I can tell is that it is much harder to get it to jump to high values, F8 or f11 might be the maximum I saw and these are already rare. When you think the diaphragm is good, put the setting in the camera back to f2.8. The aperture will stay stuck at what you set it to. The camera will say you shoot in f2.8, but in reality it is a different aperture value. This value will stay until you select a different value from f2.8 in the camera and you push the aperture button again. However even if you find your favorite aperture that way, AF will not work. It will always go from closest to infinite, never finding focus. So if you use AF, set the focus before changing the aperture. To get AF working again you need to select a different aperture than f2.8 in the camera and press the aperture test bottom on the side of the camera until the aperture is fully open (f2.8). Then AF will work again. AF will not work if the aperture is in any other position than fully open. So it is a choice between only f2.8+AF or inaccurately something between f2.8-f22 without AF and no easy way to know the real aperture without calculating it with test photos. Still helpful if you for example always shoot at infinity and want an aperture over f2.8. Just take a few test shots to determine if you get the depth of field you want. Or maybe you are lucky and your AF is not affected at the same time.

Had the same issue happen to me with my 70-200 today. After I removed and replaced it had no more problems. Shot some more later and still no problems. Canon said most likely was not seated correctly or not a good connection. But when you pay for a L series lens you expect it to work without problems unless you drop etc then that's another story. But as you said you have not dropped it and I bought mine new so I know it has never been dropped so you never know. But mine seems to be fine so I guess it was just a bad connection.

I too have this problem. Works well at 24 and 70, but when I use 60 at f/5.6 or lower, I get the error code. Very frustrating as this lens is one of my main lenses.

Mine just started doing the same thing. Sooo frustrating. And mine is the 1:2.8

Damn, you nailed this on the head. My 24-70 2.8L lens started to get this fault. I cleaned and cleaned. Fails on both my MK III and MK IV 5Ds. This lens works at f2.8. Any other setting it fails with ERR 01.

Same issue and my lens was brand new so was NOT an issue with a previous user. It is an expensive piece of glass too.

I too had the same issue, lens brand new from a well known retailer, lasted about 9 months before the same issues started, bot retailer and Canon refused to replace or fix under warrenty, lens spent more time in the post than it ever did on the camera and has yet to be repaired.

Got the 24-105L (2nd hand) been perfectly fine for more than a year in the studio. Then the error came today. Tried using the lens outdoor using natural light, and its ok. Bring back to studio and error again.

I'm also experiencing this with my canon 24-70 mm 2.8 f lens .. so frustrating how a $2400 lens can start doing this on it's own... no damage has happened to make this occur... angry I'll have to spend money to repair a problem I didn't create.

I found information that it is a faulty aperture module. The part only costs about 18 euro's. I think I am going to go down the path of repairing it myself. Found a very good youtube video about it. My lens is 10 years old and I don't have access to a Canon repair shop in Nicaragua.

Same thing happened here :( such a bummer

I have same problem on Sigma 150-600mm Contemporary. I just get an aperture of 00 and then Error 01 message. I've cleaned the contacts, replaced the battery and no good. I'll have to send it away to get repaired. I've hardly used the lens which is now out of warranty.

I have this issue on my 24-70 f2.8 since yesterday. The lens works fine when I use it with f2.8 with any focal length. If I change the aperture to any other value, it only works with 24 mm. It really bothers me, because I need it all the time obviously and now I have to use it crippled until christmas time where I have no jobs because of the holidays. Then I can let it be repaired or just get the new RF lens for my R6 (which is waaay too expensive but what can I do..)

I have that same problem develop on that same lens. After checking online, it seems it might be a thing with the Canon 24-70 f4 lens. I've just been quoted almost the same price as it cost brand new, to get it fixed! What a rip off Canon!… They should have a recall if as it seems to be happening quite a lot. I've only had it for seven years, and I don't even use it that often. Ironically it's the only lens that I've bought brand new!… 🤨

Mine has problem with the zoom ring. Definitely not the contact

Having the same issue with my 24-70 in my mark iv. I have other cannon cameras and they do not have issues with the lens. so I am going to rent a lens on monday to see if body is faulty.

similar issue here, but its only doing it on different cameras, I have a 5D3 and 7D2 and 6D, the 24-70 lens works perfectly on the 5D3 but throws error code with the other 2 cameras. I have other L lenses that work flawlessly on all my cameras, so I'm thinking it has to be an internal lens issue too. Sending lens away for a look at.

Yes my canon 7d and the canon 24-105 mm has just developed this problem,very frustrating.Have tried to clean the connectors but the problem came back again after a few shots.Very disappointed ,this is a very versatile lens but would not rely on using this lens when going on special trips abroad.Yes once again very disappointed.

same problem for me with Canon 5D MkII with USM f24-70 lens. Seems this a common quality problem from Canon.

Just got a lens and it came to me with this problem. So frustrating:(

I've owned my 24-70 f2.8L mk2, bought new, for a little over 5 years now and after some some months unused I took it out of the case today to shoot and after a few shots I got this message. So basically nothing I can do apart from forking out hundreds for a repair?

same error i faced . 24-70 .2.8 lence ....changed the Power Diaphragm 5th time in 3 years...total sad about the Product ..

I'm having the same problem with a Tamron 16-300. With a Canon 90D When I shoot at f14 I get the error to check len contact. Tried it with my 80d works fine. Very frustrating!

Yup. Same has just happened to mine. Like you, it's my most used lens. I guess I'll have to bite the bullet and send it to Canon for repair.

I have a brand new 18-55 that came with my camera that is doing the same thing. Tried cleaning contacts but it is brand new!

i have the same problem with same lens

This has started to happen to my 24-70 f2.8L mk2 lens, very frustrating indeed as it was working perfectly and did not drop it or anything. Tried all the advice about cleaning the contacts but didn't work - the contacts were perfectly clean anyway, I am not sure of the price of getting this repaired or where to even go , I am based in Spain and I went into Canon Espana once and their prices were utterly ludicrous ...

my Tamron 70-300 LD Di gives the same error at F8 or higher

I have exactly the same problem. Switch to my kit lense and everything is ok. Did you find a solution?

Thanks

I have the same fault. I also noticed that when I’m holding it facing down the lens falls to full zoom quite easily. Were they able to fix it?