How much does it cost to replace the imaging unit in my 1235cn laser printer?

Likely that the toner replacement was defective or fake.

Return it for a refund and buy from a different vendor.

Anonymous,
The error 091-932 refers to The Drum Cartridge (Y) has reached the replacement time.
Thank You,
Dell-Jesse L
Dell Social Media and Communities

This model OKI printer is not an inkjet printer, it is a color laser printer. and uses color toner cartridges.
The printer image drum unit has reached the end of its service life and this drum unit needs to be replaced.

I suggest you Google the Internet for an OKI image drum unit for your model printer, You will get various suppliers and their prices.
The image drum unit will cost approx. A$200

in shoul be scanner motor error.first see the scan light is blinking or not then open the scan lid and manualy rotate the scanner motor.if it rotate normaly then place it again and try to retest.if the problem not solved then replace the scanner mottor

You can reset the firmware by downloading the A01 (very first firmware release) and following the procedure outlined below;

I had the same problem:

Printer just clicked and panel indicated warming up. Tried all the USB stick thing and it wasn't reading it.

Search for usbprns2.exe in google, I ended up downloading it from some foreign site.

Place it on your desktop along with your firmware file xxxxx.hd

Connect the printer to your computer through the USB in the back panel.

Switch printer off wait a few secs then back on.

Press stop button - panel indicates download manager

Press stop again and "await image" appears.

On computer drag the xxxx.hd firmware file onto the usbprns2.exe.

The panel should indicate deleting addresses, then after loading addresses.

Printer reboots on its own and voila - working printer!

It is asking you to replace the scanning unit.

Sounds like the developer blades for the black toner is dirty. This can be fixed two ways:
The first way is the easiest, but most expensive is to buy a replacement imaging unit for $100+. (This is probally more than the original cost of the printer, and does not prevent it from happening again)
The second way is to take your existing imaging unit and open it to clean the blades that are dirty. It will take about 30 minutes, but you will learn a useful maintenance skill if you want to keep this printer. I have posted instructions in my Tips section. See this link, Sounds like the developer blades for the black toner is clogged. This can be fixed two ways:
The first way is the easiest, but most expensive is to buy a replacement imaging unit for $100+. (This is probally more than the original cost of the printer, and does not prevent it from happening again)
The second way is to take your existing imaging unit and open it to clean the blades that are clogged. It will take about 30 minutes, but you will learn a useful maintenance skill if you want to keep this printer. I have posted instructions in my Tips section http://www.fixya.com/support/r4120906-clean_developer_blades_samsung_clp_300 Hope this helps you.

My printer is not new, but I just replaced the PHD unit and received the same error. To fix it I had to clean the CTD sensor.

This link explains how to do that:
http://support.dell.com/support/edocs/systems/PRN2135CN/en/ug/sectiofv.htm#wp1182758

imaging unit or furnace or transfer kit attached to imaging unit needs replacement. A kit similar to this: http://www.officesupplysanity.com/home/oss/page_103490/120v_usage_kit_for_infoprint_133213521372_laser_pr.html?rid=baseIBM39V2634&utm_source=google&utm_medium=base&utm_campaign=office_supplies
may prove to be a good investment to keep your printer going.
If the cost doesn't support the value of the printer you could try to remove the imaging unit and clean it with a damp cloth and replace after dry.

The Imaging unit needs to be replaced when the drum fills up with waste toner. That's what triggers the message.