Here is a potential solution:
Thank you for contacting Canon product support. We understand that you are unable to scan with your PIXMA MX922.
Reinstalling the PIXMA MX922 should resolve this issue. Please follow these instructions to uninstall, download and reinstall the drivers:
1. Open the hard drive (Macintosh HD).
2. Open the 'Library' folder.
3. Open the 'Printers' folder.
4. Open the 'Canon' folder.
5. Send the 'BJ Printer' folder to the trash.
6. Return to the 'Library' folder.
7. Open the 'Receipts' folder.
8. Locate any items related to your printer and send them to the trash. However, leave the 'Canon Printer Drivers.pkg' file in the folder.
9. Return to the 'Library' folder.
10. Open 'Image Capture'.
11. Open the 'Twain Data Sources' folder.
12. Send any Canon files related to your printer to the trash.
13. Empty the trash.
14. Restart your computer.
Please follow these steps to download the necessary files to begin installation:
1. Visit Canon's website at: http://www.usa.canon.com/cusa/support/consumer
2. Type PIXMA MX922 in the "Enter Your Model Name" box and click GO.
3. On the Support page for your unit, click the 'Drivers & Software' link in the middle of the page.
4. Under Recommended Downloads, please click on the MX920 series CUPS Printer Driver.
5. If you agree, please place a checkmark next to "I have read and agree to the terms of the Disclaimer and wish to continue with the download".
6. Click the Download button.
7. A File Download box should appear and the file will be saved automatically.
8. Once the download is complete, click on the 'Drivers & Software' link again.
9. Under Recommended Downloads, please click on the MX920 series Scanner Driver.
10. If you agree, please place a checkmark next to "I have read and agree to the terms of the Disclaimer and wish to continue with the download".
11. Click the Download button.
12. A File Download box should appear and the file will be saved automatically.
13. Once the download is complete, click on the 'Drivers & Software' link again.
14. Click on Software.
15. Please click on the Canon IJ Network Tool.
16. If you agree, please place a checkmark next to "I have read and agree to the terms of the Disclaimer and wish to continue with the download".
17. Click the Download button.
18. A File Download box should appear. When it does, select Save.
19. When the Save As box comes up, click Save.
20. Once the download is complete, close all windows.
To install the unit for use over your network wirelessly, please follow these steps:
1. Press the <Menu> button on your PIXMA MX922.
2. Select Setup and press the <OK> button.
3. Select Device settings and press <OK>.
4. Select LAN settings and press <OK>.
5. Select Wireless LAN setup and press <OK>.
6. Select Other setup and press <OK>.
7. Select Advanced setup and press <OK>.
8. Follow the on screen prompts to complete the setup.
9. Double click [mcpd-mac-mx920-11_7_1_0-ea17_2.dmg] to install the CUPS printer driver.
10. Double click [msd_-mac-mx920-19_1_0a-ea11.dmg] to install the scanner driver.
11. Double click [mnt_-mac-4_5_0-ea19_2.dmg]. Files will extract, follow the prompts to complete installation.
12. Restart the computer.
If you are experiencing difficulties, you may view the installation process by following this link:
http://www.usa.canon.com/cusa/support/consumer/printers_multifunction/pixma_mx_s eries/pixma_mx922?selectedName=Wireless_Help
Once reintstalled, please attempt to scan.