ive had a d3 installed in my envoy for over a year now. im having trouble with my gmos-04. it has a gain control on it, and when i turn the gain up, i get great sound, but the awful alternator whine. and the ground is not the problem, ive tried grounding to every different location on the vehicle with the car running and stereo playing with no luck. ive also tried grounding the rcas on the back of the headunit. when i turn the gain control down, i have great sound with no whine, but if i turn up the volume the front speakers cut out then the back ones cut out, back and forth and so on. wondering if there is a different adapter i could try, cause i just cant find a happy medium with the gain control.

I have the exact same problem with a GMOS-04 in my 07 H3, It is driving me CRAZY.

I have a email in to Tech Support at Metra, I'll let you know when they respond!

i used to have the same problem, but I added a relay to the acc. Can't tell you why there was whine, and I can't tell you if it will work for you. But I saw a tip on adding realy to the GMOS-04 from metra.

btw, car is a 2008 Corvette