Hi Guys. I purchased my 2006 G35 sedan 6 months ago. Following is what has been happening and what All ive done.

1. About a month ago, car started to not start at random times and then after several tries it would start.
2. A few days ago it wouldn’t start at all and was making hollow starting sound. There was no check engine light but upon running codes, I got 1 transmission code P0725 - Engine speed input circuit.
3. I changed the crankshaft sensor with a duralast/autozone part.
4. Vehicle started right out and I took it for a drive. The second day it wouldn’t start again. The difference was it was trying to start for a second and then would make the same hollow sound (usual crank position is bad sound)
5. I went to Infiniti and got a new crank sensor based on VIN and installed it.
6. The car started right away but again wouldn’t start the second time.
7. I went to the dealer and this time got both cam shaft sensors and installed them.
8. The car just refuses to start and continues to make the holllow sound. I’m getting a code C1109 - Battery voltage abnormal. Upon checking the battery I’m getting 12.6 volts.

What should I do next. HELP!!!