Apple Hardware Test Error IP6M

Hi everyone

I'm only asking this here because I've completely exhausted my google-fu. I bought a used Mac Pro that's still in its warranty, and I'm getting this error from Apple Hardware Test:

4SNS/1/40000001:Ip6M-0.976

I managed to find out that the 4SNS part means it's a logic board sensor error, and that the crucial part is the IP6M bit, which in Service Diagnostic manuals points to:

PP12V_S0 MLB2 240V A Main Current

Honestly, I have no idea what that is.

Googling for this error, I found out this support page

http://support.apple.com/kb/TS4051?viewlocale=en_US

which states that "Although the diagnostic displays the alert that the hardware does not pass for this specific sensor, the computer can be considered as passing."

So, it's apparently a false positive.

This is not enough to convince me that the computer hardware is solid, specially because Apple Hardware Test cannot complete its tasks once it finds this error, so it's possible that there could be more.

I took it to an authorized Apple repair center, and they replaced the video card and a backboard panel (no idea what that is). They told me nothing about this particular error.

Anyone got more info on this? Should I be worried?

Is there any other way in which I can properly test this machine?

Also, in case I need to resell this computer, I'm at the risk of potential buyers refusing the machine due to this error. Anyone knows if updating it to Mountain Lion will fix this false positive?

System Info:

Mac Pro 5,1 - mid 2012

OS X 10.8.2

Quad 3.2

6GB Ram

Radeon 5770