My first iMac G5 20" had its logic board replaced already within its first year, 2006, under guarantee, then in 2012 this error code resulted from running the AHT. The machine finally failed to work at all. Not too keen on spending about 1,000 euros on repair, I bought an older, used iMac G5 20" in 2013. It too had had its logic board replaced within its first year. It worked well for over a year, but now, in July 2015, its logic board has failed again. So both my iMac G5s are useless! Having read all the previous posts, the cause seems to remain a mystery. Has anyone identified the real fault with this logic board? Is it the capacitor? Or is the fault in the thermal sensor of the hard drive, as carol godbout above says? Or some other component? This computer has some very desirable features, especially for running Classic applications. Fortunately, there are several firms who can repair the logic board, so they must know what the problem is. However, my local Apple-authorised agents here in France refuse...