I just took my pioneer head unit in to be serviced, I had alt whine and am pretty sure the head unit is to blame. Apparently they have a small internal fuse that is very easy to blow. My questions are:
1: The head unit is grounded to factory harness ground. Some people never have a problem with this some do. I did an ohm check and rad near zero ohms. Should I change it? And to where if I do? I checked all the metal I could find in the dash and none is common to ground so I would have to run one some distance.
2: People have suggested ground the head unit chassis as well. Is it needed? Same place as internal ground?
3: I've heard that the fuse can blow if your amp tries to ground through rca's. How can I make sure that this is not the case. I've checked with a DMM and get readings of near 0 ohms from amp ground terminal to frame. I've used a seat bolt, again some people say it's fine others are against it. Is there anything else I can meter to ensure the pico fuse won't blow again.
4: I think that one of my amp mounting screws could be touching metal, grounding the chassis. Is this a problem?
Sorry for the long post wanted to get all the info in. Thanks for any thoughts on the matters.

from the research i've done you're best off to ground the outside of the RCA as well, i'll let you know how this works when i reinstall my AVIC-N3 next week that was experiancing some real nasty engine noise in my previous vehicle.

VERY common issue with pioneers. just ground the RCA shields to the chassis of the head unit.