No Boot. No Chime. No Monitor. Green & Yellow DIAG LEDs?

Question

No Boot. No Chime. No Monitor. Green & Yellow DIAG LEDs?

Any Idea what these DIAG LEDs mean? Mac Pro fans and GPU fans spin up but no chime and never boots. Pulled power and let sit. Removed everything but stock GPU. Booting off SATA SSD in first slot. Also no screen response. Have been trying to update my bluetooth and wifi card. First card had issues so removed and got a replacement then after installing the replacement I can't boot. Removing replacement and reinstalling original cards does not help.. Pressing DIAG LED button shows Green and Yellow LEDs. Thoughts? Thanks.

Earlier Mac models

Posted on Apr 16, 2026 4:33 AM

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Answer 1

Top-ranking reply

HWTech

Community+ 2026

Level 9

75,008 points

Apr 16, 2026 10:56 AM in response to Eric Strausser

Unplug the computer & Remove the PRAM battery (press the power button for a couple of seconds as well). Reconnect power & see if it will power on properly & perhaps boot. I don't think the PRAM battery needs to be installed for testing purposes. I would test without it because you can always reinstall it for another test. I doubt this is the problem, but it is quick & easy to perform as I have seen bad batteries prevent some Macs from powering on properly.

You neglected to mention exactly which Mac Pro you have here. Here is a service guide for the 2010 model which provides some information on the diagnostic LEDs and also troubleshooting steps for various symptoms.....it sounds like you should be following the "No Video" troubleshooting steps. There are service guides for the older models available, but not for the 2012 model. I believe most of the information in the 2010 guide would apply or ve very close to that of the 2012 model at least for troubleshooting purposes.

http://tim.id.au/laptops//apple/macpro/macpro_mid2010.pdf

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Answer 2

Apr 16, 2026 7:49 AM in response to Eric Strausser

Do you have at least 3.00 Volts remaining in the PRAM backup battery (when tested in your hand, not in the circuit) ?

Coin cell, half-hidden behind the graphics card.

Use a very bright light and be certain you understand how the retainer works -- breaking the retainer will ruin your day.

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Answer 3

Apr 16, 2026 6:05 AM in response to Eric Strausser

When you attempt to power on, does the Power-on indicator flash a (small integer) code? what code?

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Answer 4

Apr 16, 2026 7:18 AM in response to Grant Bennet-Alder

Thanks Grant. Power light is solid white. No blinking. But If I pull al the RAM it blinks slow and steady. Additional note that I just noticed... if I unplug it for a bit and then plug it in it turn on automatically. But only after it's been sitting. If I boot it and unplug it and then plug it in right away it does not automatically boot in that instance. I have to press the button then.

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