I purchased my 07 350z HR 6MT in November last year and just a couple of days after purchase I came across my first CEL. The CEL that popped up was P0850 for the Neutral Safety Switch, after some research on this forum and some others I could never find a clear answer on this switch, some people said they're only in automatic Zs, some said it's the reverse light switch equivalent, so I don't know. All I do know is my reverse lights stopped working shortly thereafter. Fast forward to December/January I had 4 more CEL codes pop up, these were: P0138, P0158, P0037, P0057. The first two were for both banks of the 02 sensor reading high voltage and the last 2 were for H02S heater control circuit low. So I figured I need to add new o2 sensors to the list of stuff to buy next. However, fast forward to now none of these codes I mentioned before pop up anymore and I haven't changed a single thing. I should also mention my car does idle pretty low sometimes getting as low as 350ish RPMs but has yet to stall out. Basically what I'm getting to is now as of yesterday I had a new code I've never seen pop up on my scanner and it was P0603 PCM keep alive memory is failing. I don't have a single clue what is up with my car throwing all of these codes and disappearing to never reappear again. I did hear that a faulty/corroded battery connection could throw the P0603 code and my negative battery terminal is in really rough shape but reads proper voltage. Could that be the problem? Do I have a faulty ECU? I'm stuck and really don't have the money to go to a Mechanic right now so any input is appreciated. thank you.

 

1st fix the negative battery cable! Nissan part is expensive ( around50$) but you get what you pay for. Good source is Z1MOTORSPORTS.COM.
when you do this repair be sure to disconnect the positive batt terminal 1st, the. Then the negative term.
When putting things back together, start with the negative term, then the positive term. Also consider leaving the battery disconnected for a few minutes. That should reset your ECU.
Then drive the car and see if you get any CEL light. If you do check the codes again. And let us know.
Good luck.

 

I believe there is a reverse switch at the trans that dictates when to turn on your reverse lamps. I think the neutral safety switch is located on the transmission as well (6MT).

Did some digging while writing this. Yes, they are both located on the transmission. You may have a damaged wiring harness or faulty switch/sensor.
-Icer