You had following post previously, wondering if you ever did find out the reason. I have the exact same four fault codes on my 2005 seadoo 3D. Trying to unravel. Thanks.
"have a 2005 sea doo 3d with fault codes that I can not find in the repair manual or any info on them. I have 2 of the exact skis and took the ecm and vcm out of the good ski with no issues and installed it in the ski with the codes and now when I installed them back in the good ski the codes will not go away. I have a candoopro and reset fault codes and wrote to vehicle a few times and they still will not go away. so now I have 2 skis with the same codes and one ski has no issues and the other one still has issues. the codes are as follows
p1678
p1649
p1647
p0648