The theory of the modification is simple, connect three ground points in the PCB together. MAZ/PC-ALP has three separate ground points on it's PCB (Printed Circuit Board) to avoid chances of noise. Unfortunately, this design may generate the problem described above.
The modification itself is a piece of cake if you are familiar with
soldering, but make sure you do not solder to wrong pad also avoid short
circuit.
This is a report of what I have done and I give you no guarantee that it will
work nor it will not harm your adapter, HU or Mazda6.
Play at your own risk.
If you are not familiar with soldering, I strongly suggest you find a friend who is good at doing the job.
Turn your MAZ/PC-ALP over. Remove the bottom cover to reveal PCB. Examine the picture carefully and find THREE soldering points.
Double check the point before and after the soldering.Here is another sample picture.
Compare this carefully with what you have done.
