well I'm at 133k on my G35x and due for a inspection sticker and what do you know??? SERVICE ENGINE SOON comes on, on my way to the place!!! soo I go to Advance Auto and i get P0021 Cam Position, Over timing advance.. I replaced one like 3 months ago... How many are there? this also said bank 2!!! what does this part do also??

 

Its a cheap part, there are two of them. Best practice when you replace one is to do the other because they usually fail around the same time.

 

Ok, I had it cleared to get a sticker and have driven over 150 miles already and it hasn't come back on.. so idk.. hmm?

 

It may be failing intermittantly. I would change it out.

 

Change it. It's not hard to do.

 

Do you actually have an OBDII scanner? If so, check the "pending codes". When these is an intermittent malfunction, the code is stored here. When it happens a set frequency or repeat number of times, it becomes a real code and trips the CEL.

 

I am at 85k on my 2003 g35 and i had this same problem about 2 months ago.. My code was po345 ( Camshaft position sensor circuit malfunction - Bank 2 ). There are two cam shaft sensors and bank two is on the drivers side just on the side of the engine bay but you will have to remove some things to get to it...

At first my mechanic did not know i had 2 camshaft sensors so he changed the one on the passenger side but the hard starting issue was still there so i took it back and told him that g35 has 2 sensors. I told him to look in the engine bay towards the driver side and he found it after abt 10 mins.....My car has been fine since then

 

If it popped once it's very likely to pop again - just a matter of time.

Echo what others have said - when you change one change the other and save yourself some pain.