Can Pixma Printer/Scanners be cannibalized to act as scanners only?

I have an old Pixma MP160 & an MP190. I separated the scanner elements from the printer body, hoping to use them just as scanners, but despite severing the printer ribbons, and motor cables, the panel still refuses to operate as scanner only.

Is there any secret button-pressing combination to override the ink empty mechanism, so I can just scan with them?

Thanks