Kernel panic on startup AHT Error code T00P

I have a White 24 inch iMac, late 2006 A1200 EMC 2111, which will no longer start up properly.

Start up will progress to the gray screen with the apple, and the spinning progress wheel. This will last for a few minutes, and then there will be a kernel panic and the dreaded "You need to restart your computer ..." message.

I've run Apple Hardware Test and it came up with 4SNS/1/40000000:T00P. I repeated the test five times, and it was consistent with no additional codes. My research shows that code indicates a problem with sensing the temperature at the optical drive.

It seems that the problem could reside in three places:

1) the sensor on the optical drive

2) the cable that goes between the sensor and the logic board

3) the logic board.

In my research, I read that if the cable is disconnected from the logic board, the optical drive fan will run at full speed.

So, I disconnected the cable, and attempted to start the machine, but the computer still kernel panicked at the same time as usual.

Other pertinent info is that it will boot into firewire target disk mode and the hard drive is readable and even bootball by a mid-2009 13" macbook. I've been unable to boot it into safe mode or single user mode. I've been unable to boot it off an external drive (the 13" macbook in target disk mode.)

I'm hoping someone can tell me if there is a way to test the three possible problem areas I mentioned before. I have a multimeter, and perhaps there is a way to test for continuity that will show if any of these parts are bad. I'd sure like to be certain a part is bad before I buy a replacement.

I fear that since the computer still kernel panicked the the cable disconnected, the problem is in the logic board, but of course I'd like to hear your opinions.

I'm sorry this is so long, but I've tried to be both thorough and concise.