ERR 40
Canon DSLR Camera
Severity: ModerateWhat Does This Error Mean?
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
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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.
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Try a fully charged battery.
A nearly depleted battery may not have enough power for operations like sensor cleaning or flash charging.
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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.
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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.