Okay so I went away for about a week when I got back my battery was dead. Recharged it and when driving to the parts store the accelerator all the sudden stopped working and then the VDC, AWD, and BRAKE light came on. Then It began losing power (electrical) till it just went completely dead. Right away I was thinking an alternator but I had it towed and shop said it was just a battery and the alternator was fine after thoroughly checking the charging system (or so they say) Got my battery put in and went on my way. A day later after already driving it a few times the same thing happens again. Luckily I was only down the street from my house so I kept my foot floored on the accelerator and was able to get it home (all the lights came on again) So now i'm still thinking alternator but I need advice on what this could be. I know a common problem on the v36 is the sunroof drain leaking on one of the computer modules by the passenger footwell. Could it possibly be that? I'm completely out of ideas at this point so thanks in advance.
2008 G35x sedan
175k miles

 

Use a digital multimeter, what is the volts at the battery when it starts misbehaving? Should be about 14.5v if everything is working correctly. You may have an intermittently failing voltage regulator though, if the engine is running and you're only seeing 11-12 volts then the alternator needs replacing.

Also, clean up the alternator power wire to make sure it's not just a corrosion problem, disconnect the battery first, wire brush the connection, bolt it back on, clean up the fusible link to battery connection. Sometimes it's just corrosion on a lug that's the issue.

As for the VDC/AWD/BRAKE light on, you will have a diagnostic trouble code when those all light up, scan the car and see what the DTC is.

If that doesn't fix the issue take it to Infiniti for a 1 hour diagnostic.

 

UPDATE. Voltage while car was idling was 8 then started dropping. Turned out obviously to be the alternator was intermittently failing