Canon S400 User Manual page 182

Deep print head cleaning
Always execute normal print head cleaning first. Only when the normal
Note
print head cleaning does not correct the problem, perform deep print head
cleaning.
Open the Printer Properties dialog box, then click the Maintenance tab.
1
Click the print head deep cleaning icon in the Print Head Cleaning box.
2
Using Maintenance Functions
Using the Windows 98/95 Printer Driver 182