Nikon D90 shows ERR after battery died — is the mirror stuck?
Asked 7/12/2026
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2 answers
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My Nikon D90 stopped working after the battery died while shooting. The battery was old and only lightly charged. After fully recharging it, the camera now shows "ERR" on the top LCD. Pressing the shutter does not take a photo, although I can hear it trying to move something mechanically.
I also tried the two-button reset, but it doesn’t seem to respond. Looking into the camera with the lens removed, I see an angled part inside the mount and I’m wondering if that is the mirror and whether it should be in that position. When I press the shutter button, I can see a red light inside the mount above the angled mirror, but nothing else happens.
Does this sound like a stuck mirror or shutter problem, and is there anything I should try before repair?
Originally by Xianwen Chen. Source · Licensed CC BY-SA 4.0
Xianwen Chen
1mo ago
2 Answers
1
The mirror should be at an angle; it is reflecting most of the light up into the mirror box for the viewfinder. And the red light is probably a focus point display from the viewfinder.
When you do the two button reset the top display blinks after a couple seconds to let you know it has reset. There is also a custom menu reset option in the manual/menu.
The error code is probably related to a stuck mirror. There's a few possible causes for that and sometimes it is a relatively easy fix. If replacing the battery with a fully charged one didn't fix it the problem is likely mechanical. That might be an easy fix (search youtube for videos), or something more fatal.
Originally by Steven Kersting. Source · Licensed CC BY-SA 4.0
Steven Kersting
1mo ago
0
Generated from our catalog & community — verify before relying on it.
Yes—the angled part you see is the mirror, and it should normally sit at an angle like that. The red light you notice is likely the viewfinder focus-point display, not the shutter.
On a D90, an "ERR" message after the battery died can indicate a mechanical problem such as the mirror or shutter not completing its cycle. Since a fully charged battery did not solve it, the issue is more likely mechanical than just low power.
A proper two-button reset should cause the top display to blink after a couple of seconds. There is also a menu-based reset option in the camera menus/manual.
If the camera still shows ERR and only makes an attempted mechanical movement, a stuck mirror/shutter mechanism is a plausible cause. Sometimes this is a minor fix, but it can also be a more serious failure requiring service. If basic reset attempts and a known-good fully charged battery do not help, repair is the likely next step.
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