There are several types of PowerBook G4 Aluminum models.

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PMU reset required to restart

I have a PowerBook G4 1.25GHz.

It will not wake from sleep or start from a shutdown without doing a PMU reset.

What is the most likely problem?

Bad motherboard?

Bad PRAM battery?

Each time I reboot after a PMU reset I have to reset the time as well as re-enter my airport password.

Answered! View the answer I have this problem too

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1 Answer

Chosen Solution

Assuming you have a A-1046 G4 Powerbook which does have a PRAM battery and you are losing the time setting I would try the PRAM battery first.

PowerBook G4 Aluminum 15" 1-1.5 GHz PRAM Battery Replacement

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Thanks for your response.

It is a A1046.

I am wondering if the reason I need to reset the time setting each time is because I am doing the PMU reset.

And in fact the PRAM battery is fine.

Is there a way to differentiate this?


Remove the main battery and the power brick. Leave completely without power for 5 minutes. Then hook up the power brick and attempt powering up. If it powers up but the date is wrong-- bad PRAM. If you still need to reset the PMU disconnect the PRAM battery and try to boot. If it boots with just the date wrong--PRAM battery. Sometimes a bad PRAM battery will cause weird problems. In any case I would try the PRAM battery first due to the cost of parts factor--I always try the less expensive first in case of doubt.


+ I agree. Good start.


i finally had a chance to get back to this.

i took the laptop apart.

And the symptoms are a bit confusing.

One finding is that the coin battery inside the PRAM battery reads the requisite 3V. Does that mean the PRAM battery itself is fine or could it still be the culprit?

Once I put it to sleep and I am unable to wake it up, I am unable to shut down the machine by depressing the power button, I have to pull the power plug to get it to shut down.

(By the way I never have the external battery connected in this testing).

When I have to force a shut down or when I try to start up from a normal shutdown I have to reset the PMU before I can start it up with the Power button.

I tried to follow your advice on how to differentiate between PRAM battery and logic board but I get confused. I know it sound silly


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