Canon error U140 (ink tank cannot be recognised)
U140 and U150 mean the printer cannot recognise one of the ink tanks. On PIXMA models using CLI-8 and CLI-521 tanks, each tank has a chip that the printer reads; U140 appears when a chip is unreadable and U150 when a tank is detected but its data is invalid, typically a non-genuine tank or a tank whose chip has been damaged. The printer stops until the tank is recognised.
What causes it
- Ink tank not pressed down fully
- Non-genuine tank with a chip that the printer's firmware rejects
- Dirt or ink on the tank's chip or the print head contacts
- Tank installed in the wrong colour position
- Print head contact failure
How to fix it, in order
Work down the list and stop when the printer recovers. The steps are ordered from most likely and least invasive to last resort.
Identify the tank
Open the cover. The flagged tank's LED will be off or flashing rapidly. Note its colour.
Reseat the tank
Lift it out, confirm the orange cap is off, and push it back in at the front until it clicks and the LED lights.
Clean the chip
Wipe the small chip on the tank and the matching contact on the print head with a dry lint-free cloth. Reinstall.
Swap tanks between positions to test
If two tanks are the same shape (for example two black tanks on some models), swap them. If the error follows the tank, the chip is at fault. If it stays with the slot, the contact in the print head is the problem.
Replace the tank
Install a genuine Canon tank of the correct type. For U150 with a third-party tank, a genuine tank is the reliable fix; some compatible tanks with updated chips also work.
Reseat the print head
If the slot itself does not recognise any tank, remove the head, clean its contacts and reinstall it.
Stopping it happening again
When it is not worth fixing yourself
If you would rather not work through this alone, a printer specialist can take a look with you on a screen-share and tell you honestly whether the machine is worth saving.
Frequently asked questions
What is the difference between U140 and U150?
U140 means the tank is not recognised at all. U150 means the tank was read but its chip data is invalid, which often points to a non-genuine tank.
Can I bypass U140 with the Stop button?
No. The Stop button override only works for ink-level messages such as U163. A tank that is not recognised must be reseated or replaced.
Why do my compatible CLI-8 tanks show U150?
Their chips are not accepted by the printer firmware. Use genuine tanks or compatibles advertised as having chips for your exact model.
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