I just installed a new 4 channel speaker amplifier in my 2004 ES330 and now the volume control on the factory head unit does not work. There are a few things I haven't done yet however. I have not installed a remote wire to the amp (haven't wired it yet just used a temporary power supply to test the amp), and I haven't replaced the speakers. I'm wondering if there is a volume control wire I need to splice into or if I'm doing something wrong. I have made good connections to all of the speakers and all of them play loud and clear, I just cannot change the volume with the factory head unit. The only way to adjust the power is to turn the input **** on the back of the speaker amp. If anyone has any advice for me I would greatly appreciate it!