Installing Amp in New Audi w/Elec Diagnos

My friend has an 04 A4, and he was told that If he was to get an amp installed in his car, that it would mess with the electrical system, because when the car starts, it goes through a diagnostic to check for proper current, and the amp would confuse the computer and screw it up, so what the did is hooked up a device (I forgot what it is, I'll find out when I see him) to detect when there is current in the speakers, it would act as a relay and turn on the amp via remote wire.  Does all this make sense to anyone? Is this true?  If so, is this the best way to install an amp in this situation?  Thanks for the help!!!

He was told by whom??? The car's computer can't check for current draw off of the battery.Certified Security Specialist

Always check info with a digital multimeter.

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Untrue. I have an 05 A4.....i just dropped in my avic n1......and removed the factory amp. The 3 front speakers and the 2 rear door speakers are run off the headunit........the sub is being powered by an old mtx amp i had laying around.  So far I have had no problems with it.

Interesting.  I thought all that sounded like a bunch of crap.  I just now remembered that the Audi dealer told him about this.  I'll call him tomorrow and ask him what they used on his amp as a remote relay. 

You may have issues integrating some items in with the stcok gear due to fiber optic communication through the radio and the rest of the car,

The A4 is not fiber optic, it use CAN-BUS (digital language). So add amps to the existing factory stereo you just use an LOC after the factory amp. Or if replacing the head unit, you need to rewire around factory amp also. Jazzy