It doesn't start when the power button is pressed the led lights but when released it goes off. it does not start at all

1) Close the print head cover, and turn off the printer. While pressing the Resume/Cancel button, press the Power button. (Do not release the buttons. The LED lights in green to indicate that a function is selectable.)

2) While holding the Power button, release the Resume/Cancel button. (Do not release the Power button.)

3) While holding the Power button, press the Resume/Cancel button three times, and then release the Power and Resume/Cancel buttons. (Each time the Resume/Cancel button is pressed, the LED lights alternately in either orange or green, starting with orange.) During initialization, the LED blinks in green.

4) When the LED stops blinking and lights in green, press the Resume/Cancel button the 4 times. (Each time the Resume/Cancel button is pressed, the LED lights alternately in either orange or green, starting with orange.)

5) Press the Power button. The LED lights in green, and the
selected function is performed. (When the operation completes, the printer returns to the menu selection mode automatically.)

6) Power off then back on and test.

that indicates full waste ink pads/absorbers. to reset the counter try this:
1) With the printer power turned off, while pressing the Resume/Cancel button, press and hold the Power button.
(DO NOT release the buttons. The Power LED lights in green to indicate that a function is selectable.)
2) While holding the Power button, release the Resume/Cancel button. (DO NOT release the Power button.)
3) While holding the Power button, press the Resume/Cancel button 2 times, and then release both the Power and
Resume/Cancel buttons. (Each time the Resume/Cancel button is pressed, the Alarm and Power LEDs light
alternately, Alarm in orange and Power in green, starting with Alarm LED.)
4) When the Power LED lights in green, press the Resume/Cancel button the specified number of time(s)according to the function listed in the table below. (Each time the Resume/Cancel button is pressed, the Alarm and
Power LEDs light alternately, Alarm in orange and Power in green, starting with Alarm LED.)

any way if the absorber/pad is full, it have to be cleaned!

Waste ink full reset

These are the instructions which worked for me on my Canon pixma mp470:

1) Close the print head cover, and turn off the printer. While pressing the Resume/Cancel button, press the Power button. (Do not release the buttons. The LED lights in green to indicate that a function is selectable.)

2) While holding the Power button, release the Resume/Cancel button. (Do not release the Power button.)

3) While holding the Power button, press the Resume/Cancel button three times, and then release the Power and Resume/Cancel buttons. (Each time the Resume/Cancel button is pressed, the LED lights alternately in either orange or green, starting with orange.) During initialization, the LED blinks in green.

4) When the LED stops blinking and lights in green, press the Resume/Cancel button the 4 times. (Each time the Resume/Cancel button is pressed, the LED lights alternately in either orange or green, starting with orange.)

5) Press the Power button. The LED lights in green, and the
selected function is performed. (When the operation completes, the printer returns to the menu selection mode automatically.)

6) Power off then back on and test.

To fully reset your printer you can try this method. It works for most Canon Printers. It should solve any issues you are having.
1) With the printer power turned off, while pressing the Resume/Cancel button, press and hold the Power button.
(DO NOT release the buttons. The Power LED lights in green to indicate that a function is selectable.)
2) While holding the Power button, release the Resume/Cancel button. (DO NOT release the Power button.)
3) While holding the Power button, press the Resume/Cancel button 2 times, and then release both the Power and
Resume/Cancel buttons. (Each time the Resume/Cancel button is pressed, the Alarm and Power LEDs light
alternately, Alarm in orange and Power in green, starting with Alarm LED.)
4) When the Power LED lights in green, press the Resume/Cancel button the specified number of time(s)according to the function listed in the table below. (Each time the Resume/Cancel button is pressed, the Alarm and
Power LEDs light alternately, Alarm in orange and Power in green, starting with Alarm LED.)

Hi

Try this to reset the error.

1) Close the print head cover, and turn off the printer. While pressing the Resume/Cancel button, press the Power button. (Do not release the buttons. The LED lights in green to indicate that a function is selectable.)

2) While holding the Power button, release the Resume/Cancel button. (Do not release the Power button.)

3) While holding the Power button, press the Resume/Cancel button three times, and then release the Power and Resume/Cancel buttons. (Each time the Resume/Cancel button is pressed, the LED lights alternately in either orange or green, starting with orange.) During initialization, the LED blinks in green.

4) When the LED stops blinking and lights in green, press the Resume/Cancel button the 4 times. (Each time the Resume/Cancel button is pressed, the LED lights alternately in either orange or green, starting with orange.)

5) Press the Power button. The LED lights in green, and the
selected function is performed. (When the operation completes, the printer returns to the menu selection mode automatically.)

6) Power off then back on and test.

E5 means cartridges error - to fix press the "stop\reset" button for 5-7 seconds and then release it.

You can also try this:

1) With the printer power turned off but connected to a power source, while pressing the Resume/Cancel button, press and hold the Power button.
(DO NOT release the buttons. The Power LED lights in green to indicate that a function is selectable.)

2) While holding the Power button, release the Resume/Cancel button. (DO NOT release the Power button.)

3) While holding the Power button, press the Resume/Cancel button 2 times, and then release both the Power and
Resume/Cancel buttons. (Each time the Resume/Cancel button is pressed, the Alarm and Power LEDs light
alternately, Alarm in orange and Power in green, starting with Alarm LED.)

4) When the Power LED lights in green, press the Resume/Cancel button the specified number of time(s)according to the function listed in the table below. (Each time the Resume/Cancel button is pressed, the Alarm and
Power LEDs light alternately, Alarm in orange and Power in green, starting with Alarm LED.)

4 times----Green (Power)------Waste ink counter resetting

1) With the printer power turned off, while pressing the Resume/Cancel button, press and hold the Power button. (DO NOT release the buttons. The LED lights in
green to indicate that a function is selectable.)
2) While holding the Power button, release the Resume/Cancel button. (DO NOT release the Power button.)
3) While holding the Power button, press the Resume/Cancel button 2 times, and then release both the Power and Resume/Cancel buttons. (Each time the
Resume/Cancel button is pressed, the LED lights alternately in orange and green, starting with orange.)
4) When the LED lights in green, press the Resume/Cancel button 4 times (Each time
the Resume/Cancel button is pressed, the LED lights alternately in orange and green, starting with orange.)
5) After the function (menu) is selected, press the Power button. The LED lights in green, and the selected function is performed. (When the operation completes,
the printer returns to the menu selection mode automatically.)

1) With the printer power turned off, while pressing the Resume/Cancel button, press and hold the Power button.
(DO NOT release the buttons. The Power LED lights in green to indicate that a function is selectable.)

2) While holding the Power button, release the Resume/Cancel button. (DO NOT release the Power button.)

3) While holding the Power button, press the Resume/Cancel button 2 times, and then release both the Power and
Resume/Cancel buttons. (Each time the Resume/Cancel button is pressed, the Alarm and Power LEDs light
alternately, Alarm in orange and Power in green, starting with Alarm LED.)

4) When the Power LED lights in green, press the Resume/Cancel button 4 times, the green (power) led should be lit to reset ink absorbers.
(Each time the Resume/Cancel button is pressed, the Alarm and Power LEDs light alternately, Alarm in orange and Power in green, starting with Alarm LED.)

5)At the end of the service mode, press the Power button

1) With the printer power turned off, while pressing the Resume/Cancel button, press and hold the Power button.
(DO NOT release the buttons. The Power LED lights in green to indicate that a function is selectable.)

2) While holding the Power button, release the Resume/Cancel button. (DO NOT release the Power button.)

3) While holding the Power button, press the Resume/Cancel button 2 times, and then release both the Power and
Resume/Cancel buttons. (Each time the Resume/Cancel button is pressed, the Alarm and Power LEDs light
alternately, Alarm in orange and Power in green, starting with Alarm LED.)

4) When the Power LED lights in green, press the Resume/Cancel button 4 times, the green (power) led should be lit to reset ink absorbers.
(Each time the Resume/Cancel button is pressed, the Alarm and Power LEDs light alternately, Alarm in orange and Power in green, starting with Alarm LED.)

5)At the end of the service mode, press the Power button

You may try this to rest the 5100 error:

1) Close the print head cover, and turn off the printer. While pressing the Resume/Cancel button, press the Power button. (Do not release the buttons. The LED lights in green to indicate that a function is selectable.)

2) While holding the Power button, release the Resume/Cancel button. (Do not release the Power button.)

3) While holding the Power button, press the Resume/Cancel button three times, and then release the Power and Resume/Cancel buttons. (Each time the Resume/Cancel button is pressed, the LED lights alternately in either orange or green, starting with orange.) During initialization, the LED blinks in green.

4) When the LED stops blinking and lights in green, press the Resume/Cancel button the 4 times. (Each time the Resume/Cancel button is pressed, the LED lights alternately in either orange or green, starting with orange.)

5) Press the Power button. The LED lights in green, and the selected function is performed. (When the operation completes, the printer returns to the menu selection mode automatically.)

6) Power off then back on and test.