I have an error showing 49.4C02 on my laser printer 3700n What does this mean?

This error means: there is a problem with the laser unit. Dirty or faulty

Your print driver is set to store the print job. Unless you have updated the amount of memory that your printer has, most 3700 series do not have enough memory to do this. Check your printer settings closely. Right click on the printer icon in the control panel and select properties. Click the advanced tab and then click on printing defaults and you will see a tab called Job Storage. Make it is turned off and then apply. This should solve your problem.

Its the toner cartridge that is the same color as your smudges.

mulfunction of laser beam detector,
turn off the printer wait for a few seconds if still remain - replace laser unit.

I think that error code means a problem with the scanner/lamp. Any type of Exxx code means the machine needs (repair) service. This is a fairly new product and should still be in warranty, so I recommend you contact your regional Canon service agency.

open printer preferences, then go to color management, use manual settings, choose black only...good luck!

Hope it helps
1. A temporary printing error has occurred.
2. Press GO. The page containing the error will automatically be reprinted.
3. Reseat the connections to the laser scanner and then to the engine controller board.
4. Replace the laser scanner.
5. Replace the engine controller board.

Remove the left cover.
2 Disconnect all cable connections (19 connectors for the HP Color LaserJet 3500 series printer and 20 connectors for the HP Color LaserJet 3700 series printer).
3 Remove four screws (1) and remove the PCB (2).

disable cartridge check in DIAGNOSTICS