5C00 purge cam sensor error: solved

My MX7600 printer has a long history of messing ink while purging.
It is a pigment printer but seems to share most of the hardware with dye ink All-in-ones of the same age.

I thought have solved it by guiding the purge tube to a potty, but the wipers stayed very dirty and there is ink splashed on the timing strip.
So I did my usual cleaning by dripping some "pharmacist solution" on the pads and let purge.
Sprayed some on the wipers also (without dipping it up, maybe a bad idea).

After some pages I got the 5C00 error.

Could the sensor be dirty and does someone know where it is located ?

Continued:
I removed the top of the printer and cleaned everything around the purge unit but no avail.
After 3 light bumps (no rattles) the printer stops with the error, before the carriage is moved to the right.
So I don't think it is the sensor itself but something that is blocked.

Hi palombian, you may need to get hold of a parts manual for the printer, these printer models have no electronic parts on or in the purge unit, so the most likely place to look for the sensor would be close to the purge unit itself, a shaft or pully arm may obscure this sensor from view...

In case you don't have it already, this post has a link to the MX7600 service manual and parts catalog in one pdf file. The link is still active, I just checked it.

This picture of the purge unit is from the parts catalog page B-23. I think the small green circuit board on the side of the purge unit motor could hold the offending sensor.

Thanks !
Used the SM many times but never looked further in the parts section.

Still have a second one for parts, will try to disassemble the purge unit.
Sadly enough the only second hand available (as new, bid from € 25) is 300 km away .

According to the IX7000 manual (see attachment - where the purge unit looks the same, I even have this one for spares just in case) the purge cam sensor is in the back left, near the parking pads and wipers where all the ink mess was located.

Since these printers use the very easy to fill PGI-9 carts, same as my PRO 9500 II photo printer(s), and I have a stock of ink, I will try to keep them alive.

UPDATE:

This morning the printer started without the error , purge pump worked (as I could see in the potty).
This confirms the theory that the purge cam sensor can be blocked by ink and afterwards maybe short-circuited by cleaning liquid, and could function again after drying.
Since under the purge unit there are no electronics, the drastic kitchen sink solution proposed here:

http://www.bretabennett.com/pubstuff/utils/BAB's_Fix_for_Canon_Pixma_IP4000R_Error_Code_5C00.pdf

makes some sense.
Maybe many Canon printers were abandoned for a dirty sensor.

I will reassemble the printer housing, the time spent for cleaning was not lost.

Thanks @The Hat and @PeterBJ for thinking with me.