I have a Pioneer head unit with a Pioneer XM tuner in my 2000 TL. I have had a continuing problem that I haven't been able to solve. The head unit will periodically lose power (as in cutting off completely). Most times it will come back on immediately, albeit in demo mode. Most times all of the presets are OK, but every now and then they're erased. I have changed head units, rewired, connected power directly to the fuse box via a tap as well as tapping into the power lead in the factory harness. I do have a power filter in between the source and the head unit, but that filter is also powering my iPod which is still getting power when the head unit cuts off. Does anyone have a plan of attack before I dig back into the dash?

Thanks.