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Mac pro 2008 won't turn on  



So, I got a new gpu that turned out to be incompatible, so I removed it. When I turned it back on, it wouldn't turn on after I press the power button. It is receiving power. I can only get power through if i take the cr2032 battery out, plug it in, and put the battery back in. If I do this, then the Err A and Err B lights come on. When i press the diag button on the logic board, it gives a yellow light on the stby led. Any help would be appreciated greatly.

4 Answers

Have you tried resetting the SMC? I think that Mac Pro has an SMC. If so, it would be:

  1. Shut down your Mac, then unplug the power cord.
  2. Wait 15 seconds, then plug the power cord back in.
  3. Wait 5 seconds, then press the power button to turn on your Mac.

Thanks for taking time to help:)


I think there are other reasons why OP has such problems, but I haven't found out what the reason is.


I have the same issues. I reset the SMC memory and replaced the internal PRAM back up battery which worked before but not this time. Pressing the diagnostic button on the main board gives 2 red LEDs when it is plugged in.
Is it time to replace the power module?