Danger Will Robinson, Danger. 2 different grond points for the Rio and the sled? That's a potential issue right there. You should also never grounf a head unit to any point in the trunk. Dont run long ground wires. Always make sure your grounding wires are at least as thick as your 12v wires. Keep them as short as possible. Keep a common ground if possible (in the case of using amps, keep those grounded in the trunk and HU's grounded together in the front). In your case, ground all Rio parts and Sony to the same place in the dash area. The original factory ground point may not be good. Make sure you have bare metal contact with a quality piece of metal. Bruno