How do I replace the waste ink pad on my Canon S400 printer?

I just had this same problem, and came here to figure out what to do about it. Turns out I had the CD/DVD tray in the out position, so all I had to do was flip the switch to stow it and the flashing lights stopped. Maybe it will work for you as well.

CANON WASTE TANK RESET CODES

Canon S9000, S300, S400, i550, i560, i850, i860, i865, i9100, i9950, PIXMA iP3000 above,
1. Turn off printer
2. Hold down Resume button and press Power button.
3. Keep holding down Power button and let Resume button go.
4. Press Resume button 2 times then let BOTH buttons go.
5. Green lights will flash and then stop blinking.
6. When green lights are solid, press the Resume button 4 times.
7. Press the Power button and the printer should turn off, if not, press the Power button once more.
8. Your printer should respond as normal.

You can try this....

1. Turn off Canon S300, S400, S9000 Printers
2. Hold down Resume button and press Power button.
3. Keep holding down Power button and let Resume button go.
4. Press Resume button 2 times then let BOTH buttons go.
5. Green lights will flash and then stop blinking.
6. When green lights are solid, press the Resume button 4 times.
7. Press the Power button and the printer should turn off, if not, press the Power button once more.
8. Your Canon S300, S400, S9000 Printers should respond as normal.

But this happens because the waste tank is full. You need to locate it and use a paper towel to absorb the waste ink. Whenever the printer cleans itself ( when a new cartridge is installed, for example) some ink is cycled into this chamber. So if you reset and it is full, overflow may occur.....

Inkjet printers have a fibrous pad inside them that collects the waste ink from cleaning the print head. Over time, this pad fills up with ink and can no longer hold any more. When this occurs, the printer indicates a "waste ink tank full" error.

The flashing orange and green alternately light indicates that the error the printer is experiencing requires it to be sent into an authorized canon service facility.

Replacing the waste ink absorbtion pads is something the service facility can take care of for you. Once they are replaced, it'll be functional again.

Inkjet printers have a fibrous pad inside them that collects the waste ink from cleaning the print head. Over time, this pad fills up with ink and can no longer hold any more. When this occurs, the printer indicates a "waste ink tank full" error.

Replacing the waste ink absorption pads is something an authorized canon service facility can take care of for you. Once they are replaced, it'll be functional again.

An error has occurred in the printer. The number of flashes indicates the type of error, as outlined below. Check the cause and take the appropriate action.
Two flashes: Out of paper or paper feed error
Replace the paper correctly and press the RESUME/CANCEL button.
Three flashes: Paper jam
If paper has jammed in the printer, clear the jam, replace the paper in the printer correctly and press the RESUME/CANCEL button.
See Paper Jams
Four flashes: Empty ink tank
If you press the RESUME/CANCEL button, it will continue printing with an empty ink tank. However, when printing is finished, replace the ink tank immediately. If you continue printing with an empty ink tank, it will be a cause of trouble.
See Replacing an Ink Tank
Six flashes: No print head installed
Install a print head.
Seven flashes: Defective print head
Contact a Canon service representative.
Eight flashes: Waste ink tank almost full
The printer has a built-in waste ink tank for the ink used during print head cleaning. Eight flashes indicates that the waste ink tank is nearly full. Press the RESUME/CANCEL button to cancel the error so you can continue printing. Before the waste ink tank becomes completely full, contact a Canon service representative.
Note
Canon recommends to call for service as soon as this error occurs. Once the waste ink tank becomes completely full, printing will no longer be possible.
POWER lamp flashes alternate green and orange:
An error that requires contacting a Canon service representative may have occurred.
Turn the printer off and unplug the printer from the power supply. Plug the printer back in and turn the printer back on.
If the problem remains, contact a Canon service representative.

If both lights are flashing, it means the Waste Ink Pads in your printer are saturated with ink and the waste ink "protection" counter has exceeded its limit. The Waste Ink Pads should be replaced as soon as possible. You can restore your printer to a working condition immediately by using the SSC utility - download from

http://www.ssclg.com/epsone.shtml

and use it to reset the Protection Counter. This will stop the lights flashing and restore normal operation.

However, remember that eventually ink will overflow from the waste ink area and make a dreadful mess, so you must change the waste ink pads before this happens. This requires the disassembly of the printer.

If you decide to have a go at replacing the ink pads yourself, report back and I will provide further help.

If both lights are flashing alternately, it means the Waste Ink Pads in your printer are saturated with ink and the waste ink ("protection") counter has exceeded its limit. The Waste Ink Pads should be replaced as soon as possible. You can overcome this problem temporarily by using the SSC utilit to reset the Protection Counter. This will stop the lights flashing and restore normal operation.

However, remember that eventually ink will overflow from the waste ink area and make a dreadful mess, so you must change the waste ink pads before this happens. This requires the disassembly of the printer.

If you decide to have a go at replacing the ink pads yourself, report back and I will provide further help.

This may be worth a try
Canon S9000, S300, S400, i550, i560, i850, i860, i865, i9100, i9950, PIXMA iP3000 above,
1. Turn off printer
2. Hold down Resume button and press Power button.
3. Keep holding down Power button and let Resume button go.
4. Press Resume button 2 times then let BOTH buttons go.
5. Green lights will flash and then stop blinking.
6. When green lights are solid, press the Resume button 4 times.
7. Press the Power button and the printer should turn off, if not, press the Power button once more.
8. Your printer should respond as normal.

The tank is situated on the RHS.
The Print Head rests there when not in use.
Open the flap to expose the Print Head,slide the Print head across to the left.
On the area where the Print head rests, there is a black plastic square of plastic which contains 2 narrow vertically positioned ink pads.This is also spring loaded.from underneath.
The pad on the left is for BLACK the other Color.
These become saturated with ink during the cleaning process.
I suspect the Print Head has a built in sensor to detect overloaded waste tank.
The pad can be removed this by hooking it out, sideways.
Unless the pads are leaking ink everywhere I wouldn't remove it.
Use Cotton Buds to soak up the excess ink. I used about 15.

Then.....
Turn off printer
Hold down RESUME button and press POWER button.
Keep holding down POWER button and release RESUME button.
Press RESUME button 2 times, then release BOTH buttons.
The GREEN light will flash and stop flashing.
When the GREEN light goes out, press the RESUME button 4 times.
Press the POWER button and the printer should turn OFF
If not press the POWER button once more.

My experience was when turning the printer on at a later date the POWER and RESUME lights still flashed.
All I did was press the RESUME button and the printer operated as normal.