ERR 40
Canon DSLR Camera
Severity: ModerateWhat it means
ERR 40 means the camera detected a power supply problem.
The battery may be depleted, making poor contact, or the battery grip is not communicating properly.
Remove and reinsert the battery, or try a different battery.
Affected Models
- Canon EOS Rebel series
- Canon EOS 5D
- Canon EOS 6D
- Canon EOS R series
- Most Canon cameras
Common Causes
- Battery nearly depleted — not enough power for the operation
- Battery contacts dirty or corroded
- Third-party battery not communicating properly with the camera
- Battery grip connection issue
- AC adapter problem (if using mains power)
How to Fix It
-
Remove the battery, clean the contacts, and reinsert.
Use a dry cloth to clean the gold contacts on the battery and inside the camera.
Make sure the battery clicks securely into place. -
Try a fully charged battery.
A nearly depleted battery may not have enough power for operations like sensor cleaning or flash charging.
-
If using a battery grip: remove it and test with just the camera body.
Battery grip connections can cause power errors.
Clean the contacts between the grip and camera. -
Use a genuine Canon battery instead of a third-party one.
Some third-party batteries lack proper communication chips.
Canon cameras may reject them with ERR 40.
Frequently Asked Questions
Can third-party batteries cause ERR 40?
Yes.
Canon cameras communicate with the battery's chip.
Some third-party batteries have incompatible chips, triggering ERR 40.
High-quality third-party batteries (Wasabi, Neewer) usually work fine.
Does ERR 40 mean my battery is dead?
Not necessarily.
ERR 40 can be caused by poor contact, not just a depleted battery.
Clean the contacts before buying a new battery.