How To's

Canon’s Error 99: the Man, the Myth

Published December 31, 2008

The LensRentals Error 99 Process

This is based on Canon’s technical support suggestions, with a couple of additions we’ve made as we gained experience.

First, we pull a “tech support” reboot.

  1. Turn camera off.
  2. Remove battery.
  3. Replace battery.
  4. Turn camera on.
  5. Try a shot.

Sometimes that works. If not then a full reboot:

  1. Turn off the camera.
  2. Remove the lens, battery, date-time battery (see below), and CF card.
  3. Allow the camera to sit without power for approximately 20 minutes with the power switch “on”. Recharge the battery during this time. (Full disclosure here: somebody once suggested the 20 minutes and power switch on part, we want to top off the battery anyway, and we’ve generally got other stuff to do so we do it this way. Waiting 30 seconds and using a different, fully charged battery would probably be just as good, but this is what we do.)
  4. Turn off the camera, replace the backup battery, insert the fully charged battery, turn on the camera.
  5. Press the shutter button to check for Err99.
  6. If Err99 occurs, remove the battery, examine and clean the battery and camera connections. If at all possible, try a different battery.
  7. If Err99 still occurs, use the manual sensor cleaning function to raise the mirror and open the shutter. If the shutter does not completely open, it is the source of the problem. If a leaf is out of alignment, some people have reported using a soft brush to move the shutter leaf back into place. Personally, I’d send it in for service.
  8. If Err99 still occurs, the camera almost certainly needs service. You might try reinstalling firmware, but it’s unlikely to work.

If there’s no Err99 after the above, the next step is to check the storage system:

  1. Insert and format CF card, then press the shutter button as you would to take a picture.
  2. If Err99 try a different brand and size of card. If no Err99, the problem was the card and you should be done.
  3. If Err99 still occurs with a different card, the problem is with the camera’s card connections, and repair will be necessary.

Finally, check the lens:

  1. Turn the camera back off.
  2. Gently clean the contacts on both the lens and the camera (see Note #2 below)
  3. Remount the problem lens, set to manual focus, IS off, widest aperture and take a picture.
  4. If no Err99 with everything off, activate autofocus, then IS, then stop the aperture down, taking a picture to confirm no ERR 99 after each step.
  5. If Err99 occurs, try a different lens. If only one lens is a problem, that lens needs servicing. You’ll get better service results when you can be specific: i.e. “Err99 only when IS activated, etc.” in your service request.
  6. If Err99 occurs with more than one lens, and no other cause is apparent, the camera needs to head to Canon for repair.

Note #1: Some Err99 problems occur only with the camera in certain settings: i.e only in Av mode, or only in AI servo. In these cases, repair is almost certainly needed.

Note #2: I know first-hand that Canon Service Techs use the “gently rubbing a clean pencil eraser” technique of cleaning the electrical contacts. I also know that knowledgeable electronic engineers state this is a bad idea, that the friction could wear out the gold plating on the electronic connections, leading to corrosion. Radio Shack and other electronics stores sell electrical contact cleaning solution that can be used with a Q-tip or soft cloth to clean the contacts as an alternative. I’m still using the eraser; I figure if rubbing metal contacts across each other every time I change a lens isn’t wearing out the coating, the pencil eraser sure isn’t.


I know this has been an overly long and probably not-very-useful essay, but it’s a topic I really got into. I certainly will have made some omissions or mistakes in something this long and complex. I welcome corrections and suggestions from any of you with different experience in this area and plan on updating and upgrading this piece as I get more input.

Author: Roger Cicala

I’m Roger and I am the founder of Hailed as one of the optic nerds here, I enjoy shooting collimated light through 30X microscope objectives in my spare time. When I do take real pictures I like using something different: a Medium format, or Pentax K1, or a Sony RX1R.

Posted in How To's
  • Butch Teel

    Thanks for nothing. I don’t see anything in your post which is positive except saying nobody knows what error code 99 is supposed to indicate. I have a stock Rebel XT. I have tried removing the lens and then putting it back on; I’ve checked the pins for the storage disc (which gave me an error of (0). I’ve tried to reformat but that gave me the error 99 which led me here.

  • Tango GF

    Thanks a lot for your help, everything seems to work, I’m new to the camera, it’s already used and I was very sad because I thought I had broken it, and your article served me a lot

  • cleaning the lens contact worked for me…ty

  • It sounds like a shutter replacement is going to be required, I’m afraid.

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