Canon Printer Error B204 — What It Means & How to Fix It

What Does This Error Mean?

Canon error B204 is a serious hardware error — usually a printhead failure or main board fault. The printer has detected an unrecoverable internal error and has stopped to protect itself from further damage. This is one of the more serious Canon error codes and often means the printer needs professional service.

Affected Models

Canon Pixma MX922
Canon Pixma MX892
Canon Pixma MG6320
Canon Pixma MG7120
Canon Pixma iP8720

Common Causes

The printhead has shorted internally due to severe ink flooding or age-related failure
Ink has leaked internally and reached the main circuit board, causing a short circuit
The printhead's heating elements have failed, triggering a critical thermal fault
A power surge damaged the printer's main board or the printhead driver circuit
The printer has operated far beyond its rated duty cycle, causing cumulative hardware degradation

How to Fix It

Turn off the printer and unplug the power cord. Wait at least 10 minutes. This allows any internal faults caused by temporary conditions to fully reset.

A small number of B204 errors are caused by temporary electrical spikes or printhead overheating rather than permanent hardware damage. A full power cycle is always worth trying first.
Remove all ink cartridges. With the printer unplugged, gently move the printhead carriage to the center of the printer manually. Look for any signs of ink flooding — pooled ink under the carriage is a bad sign.

Ink pooling under or around the printhead area suggests a severe leak that has likely already damaged the main board.
If no obvious damage is visible, reinstall the cartridges and reconnect the power. Turn the printer on and observe whether the error returns immediately at startup or only after attempting to print.

If the error appears immediately at startup every time, the printhead or main board has a permanent fault.
Try replacing the printhead if you can obtain one for your model. For Canon Pixma Pro and high-end MX/MG series printers, replacement printheads are available for $60 to $120 and are relatively straightforward to swap.

A printhead replacement is the most likely fix if there is no visible ink damage to the main board.
If replacing the printhead does not resolve B204, the main board has likely been damaged. Contact Canon support or a local printer repair center for professional service or to discuss replacement options.

Canon support can sometimes offer discounted replacement printers or repair vouchers for models with known hardware issues.

When to Call a Professional

Error B204 is a serious error that almost always requires professional diagnosis. If your printer is still under warranty, contact Canon immediately — this type of fault is typically covered. Out-of-warranty repair costs can range from $80 to $150, which may exceed the printer's current value. Weigh repair costs against the price of a comparable replacement printer before committing.

Frequently Asked Questions

Is error B204 always fatal for the printer?

Not always — some B204 errors are caused by a temporary fault and clear after a full power cycle. However, if the error returns consistently, it almost always indicates a permanent hardware failure in the printhead or main board. There is no software fix or driver update that can repair physical hardware damage.

Can ink flooding cause error B204?

Yes — ink flooding is one of the most common causes. If ink has leaked out of the cartridges or printhead and pooled inside the printer, it can create short circuits on the main board. Always check for signs of ink overflow when diagnosing B204.

Is it worth repairing a Canon MX922 with error B204?

The Canon Pixma MX922 was a mid-to-high-end printer when new. If a printhead replacement clears the error, it is generally worth it — the printer is otherwise capable. If the main board is damaged, repair costs will likely exceed the printer's current secondhand value. Compare repair quotes with current prices for a used or refurbished replacement.