Err99 is a catch-all code that has become the go to for fatal errors on Canon SLRs. You can read the history here, but Err99 can indicate a number of different issues including lens contact issue, battery failure, main board failure, as well as in the case of this Canon 30D, Shutter failure.
Some solutions you can try at home:
- Clean the lens contacts and attach a new lens
- Try a new CF card
- Remove the time/date battery and the main battery. Replace the main battery with a new battery after 30 minutes.
If none of these solutions work, it indicates either failure with the main board, or the shutter, which would need to be professionally replaced by a technican. For help with your Canon SLR Repair, feel free to call our service center (323) 887-0777.