MacPro 3,1 Motherboard Component, 4MOT/1/40000002: IO-O trouble

[ColdCase]

My trusty 3,1 (2008) locked up while playing a video. The machine will boot into recovery and run disk diagnostics but doesn't seem to want to run any OS (I have a spare USB boot drive). It gets to the light blue screen and a progress wheel but seems to be stuck there, restarting the wheel every 5 seconds. I don't get a chime.

So I was going through the troubleshooting process pulling extraneous components and thinking perhaps a weak power supply, bad drive, PCI card. All the motherboard diagnostic LEDs are OK.

While pulling the video card, one spring clip holding the heat sink on the component in the center of the image attached pulled away from the mother board (the U hold down pulled out of the motherboard). Seems like the graphics card was holding the heat sink on so it didn't fall off completely.

I've been trying to locate a component layout of the 3,1 (2008) motherboard so I could understand what that component does and could it possibly be causing the symptoms.

Dunno if its worth thinking about repairing the hold down or just replace the motherboard..... it may help if I knew what that component does.

I'm going to guess I'll need a motherboard if I choose to keep this machine running, but thought I'd check in here as there always seems to be good advice.

Thanks

 

[adam9c1]

My guess it's the south bridge.

 

[ColdCase]

I removed all drives and peripherals except the CD drive and the video card as that was holding the heat sink clip for the chip. Ran a short hardware test and came up with 4MOT/1/40000002: IO-O during the motherboard test. I did a quick google search on it and came up with nothing specific, except that 4MOT is fan related. IO-O is the fan name, I think as others mention things like exhaust fan. Could the front Fan Assembly be "IO"? The exhaust and PS fans seem to be running, but not the ones in front fan assembly. Dunno if they are suppose to be during AHT.

Any other clue here? Gathering from other posts around the net, it seems to be either the fan, motherboard or dust (its pretty clean)

 

[ColdCase]

I may just order a $25 fan, seems easier to change than the logic board

 

[MIKX]

Southbridge, Northbridge rarely fail unless you have tinkered with them ( I have and paid the price ! ) or yu have never de-dusted your cMP

I suggest. . .( 1) Use another HDD. ( 2) remove all other HDD's ( 3) reboot to NVRAM reset ( Command key + Option + P + R . . but .. . hold the keys down until you hear the "Happy Mac chime TWICE.

3. Check to see if there are any abnormalities.

4. Upgrade to the OSX version of your choice ... but. . only use the downloadable "Combo" downloads.

Hope it goes well for you.

 

[ColdCase]

Thanks, reseting NVRAM allows me to boot from my backup drive. The computer seems to work fine but the front fans don't spin. I've been looking at fan replacement threads

 

[ColdCase]

To follow up, I replaced the front panel fans and boot drive and things seem to be working fine. I got a little scare when I put everything back together and the fans still wouldn't spin up. I started looking for mother board options. But on third glance I found the fan enclosure didn't get seated properly, a little persuasion fixed that. I'll have to let it run for awhile and see how it goes.