iMac G5 shuts down from Sleep mode

Same thing's been happening with my late 2004 iMac G5 10.4.11 When I try to wake it from sleep using the keyboard or mouse, it shuts down. Starts back up okay. I ordered and yesterday received an internal backup battery which "they" say needs replacement after 5 years and can affect start-up. My iMac is almost 5 years old, so I thought I'd try replacing the battery. I've reset the SMU--didn't help with the wake up/shut down problem. Anyone else? Thanks.

Hi John & easycat3, and a warm welcome to the forums! 🙂

Boot off your Install Disk while holding down the *d key*, (not c key), then run the extended Apple Hardware Test. Some disks require you to use the Option key at bootup to select AHT. Some models have a separate AHT CD. I think all G5s came with separate AHT CDs.

Thanks, BDAqua for the quick response. I'll boot, as you suggest, with the G5 iMac's original AHT disc, run a test and hope for the best. Installed new internal backup battery last night, no surprise; did not solve the wake up = shut down problem.

Okay, AHT shows error with one of my two 512 memory modules. Since memory prices are more reasonable than they were in 2005 I may replace the two-512s with two-1GBs. Any suggestions about running the iMac until I get the memory replaced? This wake up/shut down process is bothersome, but is it likely to cause other problems in the meantime? Thanks for your help.

is it likely to cause other problems in the meantime?

Yes, likely Disk corruption, I'd run with just the one good stick of RAM, unless that model requires 2 equal sized sticks.

Thanks for the advice. Standard equipment on this iMac was one 256 module, the other slot empty. I'll remove the bad stick. Thanks, again.

Good luck, do let us know how it's going! 🙂

Mission accomplished, bad 512 module removed. System Profiler recognizes 512 MB in slot 1 and says slot 2 is empty. Did one wake up after only a few minutes in sleep mode. . .no shut down. So far, so good. No difference in speed with the bad stick removed. Guess I've been limping along on 512 for some time now.
Thank you very much for your expert advice, BDAqua!

Thanks for the report! 🙂

Since removing the bad stick, I find that Ms. iMac doesn't mind waking up after a short nap, maybe 5 minutes. When she's been in sleep mode for 90 minutes or so, a wake-up call sends her into shut down. Wonder if it would help to reset the SMU. Open to suggestions. Thanks!

You generally want do that or a PRAM reset after a change in Memory, I'd also get Applejack...
http://www.versiontracker.com/dyn/moreinfo/macosx/19596

After installing, Reboot holding down CMD+s, (+s), then when the DOS like prompt shows, type in...

applejack AUTO

Then let it do all 5 of it's things.

Also, 512 MB is pushing Tiger on the low side! 🙂

The 5 things it does are...

Correct any Disk problems.
Repair Permissions.
Clear out Cache Files.
Repair/check several plist files.
Dump the VM files for a fresh start.

I have an early iMac G5 as well. Resetting the SMU is worth trying, but I hope you don't have a hardware problem. Early iMac G5's are notorious for having power supply failures which can lead to SMU/sleep/shutdown issues. Apple provided a [recently-ended|http://www.apple.com/support/imac/repairextensionprogram> 3-year repair extension program for early iMac G5s with power-related problems, and I ended up needing two replacement power supplies and a replacement logic board for mine.

There have been a number of discussions about iMac G5 shutdown issues, including suggestions for replacement hardware components if needed, at the iMac G5 forum here:
http://discussions.apple.com/category.jspa?categoryID=134

This is great--having Mac Mavens at my fingertips. Thank you. I'll do the SMU/PRAM reset and get/run Applejack.

Thank you jsd2 for the great info on power supply. I will seriously look into the 3-year repair program. (Apple already replaced my logic board & power supply at a month over the one-year warranty--no charge.)

I will also take a look at:
iMac G5 forum here:
http://discussions.apple.com/category.jspa?categoryID=134
per your suggestion.

Thank you.

I will seriously look into the 3-year repair program. (Apple already replaced my logic board & power supply at a month over the one-year warranty--no charge.)

Unfortunately, the three year repair extension program has now ended-
http://www.apple.com/support/imac/repairextensionprogram/
(but now you know why they fixed yours for free earlier, even though it was out of warranty 🙂 )