my Canon EF-S 18-55mm f/3.5-5.6 IS STM just stopped communicating with my DSLR (Canon EOS 77D). Furthermore, I can't even use manual focus anymore.

Right before this happened, I tested some extension tubes for macro photography. One of those extension tubes did have some wiggle room and did not click in-place correctly. I then got the following error message when taking a photo with this particular extension tube:

Err 01
Communications between the camera and lens is faulty. Clean the lens contacts.

Since this moment, my lens isn't communicating with my DSLR anymore. Maybe it's just a coincidence as correlation doesn't imply causation.

What I've tried / discovered so far:

  • I've tested another lens on my DSLR (working) and my lens on another DSLR (not working) => The lens is broken, not the DSLR. Phew.
  • When testing the lens-camera-combinations, I noticed that my lens produces a super-high-pitched and barely audible electrostatic noise while the other lens (Canon EF-S 55-250mm f/4-5.6 IS STM) does not.
  • I suspected that the extension tubes' connectors damaged my lens' connectors. When examining the lens' connectors, I did not find any damage though as they seem perfectly fine and the extension tubes' connectors contract as expected when pressed on.
  • Next, I cleaned the lens' contacts with cleaning alcohol on a cotton swab and also wiped them with a microfiber cloth.
  • The aperture is displayed as F00 (immutable) and my camera is unable to use autofocus with this particular lens.
  • I then covered the large connector (also tested covering both of the non-elevated connectors) with a piece of tape in order to test whether I'd be able to shoot with manual focus and fixed aperture. With this workaround, I was able to take a picture without getting Err 01.
  • But, I was unable to focus, even manually (switched to MF on my lens).

What else could I try? What might be broken and how could I fix that?

I'm not a fan of taking the lens apart if potentially unnecessary, but --- assuming I know what I'm looking for --- I'd be willing to do that.

Lens' connectors with tape over largest connector. Aperture displayed as 00. Extension tubes. Extension tube's pins.

  • \$\begingroup\$ When you were testing the extension tubes: Did you always disconnect the the tube(s) from the camera before attaching/detaching the lens from the tube(s)? \$\endgroup\$
    – Michael C
    Oct 1, 2020 at 13:45
  • \$\begingroup\$ @MichaelC no, I didn't. Should I have done that? I always turned off the camera though. But the lens didn't always click in place correctly on the connection tube as the connection tube(s) connectors had a little bit of play, so this might have yielded a result similar to detaching the lens from the tube(s) without disconnecting the tube(s) from the camera first. \$\endgroup\$
    – jbh168
    Oct 1, 2020 at 15:29
  • \$\begingroup\$ Canon always recommends attaching lenses to extension tubes and extenders/TCs before attaching the back end of the tubes/extenders/TCs to the camera. Even when the camera is turned off there is still some minimal power flowing to monitoring things. I do not know if that includes the lens mount. But if you insert a battery with the camera turned off, the "memory card activity" light will light up for a few seconds as the camera checks the status of any inserted memory card. \$\endgroup\$
    – Michael C
    Oct 1, 2020 at 16:24

1 Answer 1


Unfortunately Err01 is a generic error that tells you nothing about what's wrong. Some command sent to the lens isn't getting a valid response.

I would be surprised if the use of the extension tube had anything to do with it. After all, the lenses are designed to have metal contacts dragged across them, shorting contacts, etc. on a daily basis. They have to be designed to cope with any amount of play in the contacts.

The reason you aren't able to focus is that STM lenses are typically focus-by-wire, i.e. the lens's electronics are adjusting the focus based on electronically sensing the position of the focus ring. If the electronics are misbehaving for any reason, that won't work.

The fact that the focus and aperture are both down, as opposed to just one, suggests maybe the lens's control board is dead.

That said, the pre-STM 18-55 lenses were prone to the ribbon cable between the control board and the aperture tearing. It's possible that Canon never fixed that design problem, and that the electronics just won't do anything if they can't control the aperture. It's hard to say.

When you zoom the lens in and out, do you hear a dragging? If so, it's probably a torn ribbon cable. If not, the electronics are probably shot. But without tearing apart the lens, it's anybody's guess.

Either way, I'd probably suggest taking this as an opportunity to trade out the kit lens for something more robust, like the 15-85 (or even its predecessor, the 17-85, which you can find for maybe twice the cost of replacing your kit lens with the same model).

  • \$\begingroup\$ Yeah, I figured that Canon's developers skipped the class on useful error messages. Thanks for all the insights into the lens' internal workings! And it's nice to hear that the extension tubes might not have had anything to do with my lens' failure. I'll probably avoid them despite that though, just to be safe. I do not hear more dragging than what's probably typical for such a lens (similar amount of dragging compared to that of the other lens). If it's the electronics, the lens is probably lost anyways, isn't it? So I might as well open it and see if I can make anything out in there... \$\endgroup\$
    – jbh168
    Oct 1, 2020 at 12:33
  • \$\begingroup\$ @dgatwood The way the interface is designed, the first pin to break contact is the main 6V power pin, which is on the far left as one faces the camera. As the lens is rotated off the camera all of the lens contacts move to the right away from that far left pin and none of the lens' contacts, except the one that is in contact when the lens is locked in place, ever touches the 6V pin. If an extension tube had shorts in it that crossed one contact with another, it's possible that could fry the lens' main board. \$\endgroup\$
    – Michael C
    Oct 1, 2020 at 16:32
  • \$\begingroup\$ Likewise, the +5.5V pin that powers the digital communication is the first of the non-elevated pins. It is recessed on the body,along with all of the other data pins, so that the 6V contacts on the lens, recessed on the lens, won't touch anything as they pass above the 5.5V pin as they are rotated off the camera. All of the other data pins are to the right of the 5.5V pin and the lens contacts for those never touch it as they rotate away from it. \$\endgroup\$
    – Michael C
    Oct 1, 2020 at 16:39
  • \$\begingroup\$ My point was that I don't think that the mount having a little bit of play is likely to cause any kind of meaningful short, for all the reasons you mention. But also, 5.5V is within the voltage range that TTL pins are required to tolerate anyway, so even if it did short internally, it shouldn't cause any damage, just incorrect data. You'd pretty much have to swap power and ground before I'd be worried about damage, and I can't imagine the tube doing that. \$\endgroup\$
    – dgatwood
    Oct 1, 2020 at 19:14
  • \$\begingroup\$ And yeah, the lens is probably lost anyway. I mean, you can probably replace whatever has failed, so long as it doesn't require removing any screws that affect the positioning of the optical elements, but I don't know the interior of that lens to say whether that is possible or not. With original 18-55 lens, you actually had to unscrew the front lens element just to get into the thing. :-/ It was a pain to re-ribbon that lens. \$\endgroup\$
    – dgatwood
    Oct 1, 2020 at 19:17

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