Temp sensor iMac G5 - reads low

[squelch41]

Hi,
I've got an original 17" imac G5 and seem to have the opposite problem to everyone else with it!
The fans dont spin up fast enough under load and, eventually the system will suddenly enter sleep.
This all seems like overheating.

If use software to find the CPU T-Diode temperature, it reports 1.4C which is obviously wrong.
On the Apple Hardware Test, I get a error of 2STH/1/3:CPU-Tdiode

At times, the system does read the temperature - it will sometimes show use usual 50-73Cish and the fans ramp up and down accordingly.

I assume there is a faulty temperature sensor but I don't know where the CPU-Tdiode sensor or traces are -- are they internal to the CPU or is it on the logic board itself?

The capacitors on the logic board all look good and they system runs fine otherwise.
I've tried resetting the SMU but that made no difference.
The HDD temp sensor works

Any pointers would be great.
Would rather try and repair if I can rather than replace logic board.

 

[NewbiePPC]

I believe that it's a diode on the logic board or the CPU itself, nobody seems to know where it's.

I think you best bet it's to modify the kext to ramp up the fans, not ideal but better than replace the logic board for a machine that it's for thinkering or occasional use.

 

[squelch41]

I believe that it's a diode on the logic board or the CPU itself, nobody seems to know where it's.

I think you best bet it's to modify the kext to ramp up the fans, not ideal but better than replace the logic board for a machine that it's for thinkering or occasional use.

Thanks, I tried modifying the kext but, even when the sensor was working (which it does randomly!) , it doesnt make any difference to the fan speeds or when then cut in or out.
Interestingly, running "sudo kextunload -b com.apple.driver.AppleFan" doesnt ramp up the fans either making me wonder if the AppleFan driver isnt in play for the iMacG5?

In fact, running sudo kextstat, there is no mention of AppleFan being loaded