Nissan guys: EVAP Purge never requested

[CBR.worm]

'06 G35 6MT w/ VQ35DE Revup.

I have a fuel smell coming from the Evap canister most of the time. There are no CEL's. The valve at the canister was replaced at around 90K due to P0456.

If I command the purge valve to open using CONSULT II, it will open the specified duty cycle and pull the fumes out of the canister. If I log data while driving over hundreds of miles, the purge valve is never commanded to open. I can drive for a day or two with the valve commanded open and the fuel smell will go away for a couple hundred additional miles.

I have another '06 Infiniti, if I log data while driving, basically anytime the engine is up to temp and I am off idle, the purge valve is open some percent.

I have verified that the valves all work properly, there are no leaks, the pressure sensor was swapped between vehicles and made no difference. And there are no CEL's or stored codes. It has been like this for about 10K miles and never a code.

What am I missing, I assume there are other things that need to be ready. The ECU reports correct engine and air temp, the car runs fine. The ECU reports throttle closed, % and WOT properly.

Is there a common thing that would cause this?

Thanks!

 

[punisher]

At some point your vehicle has to do an evap system self test (OBD Readiness Monitor) to verify system integrity. Certain factors determine when/if the test occurs. Temperature has to be between certain points (you verified this), the fuel level must be between certain levels etc. Hard to imagine you can go thousands of miles and not have an EVAP code. Is there a fuel level input to the PCM?

It is odd that it will open the valve when commanded, yet not open it on its own during regular driving. You got a tough one. You have done all of the diagnostic steps I would have attempted. You know the circuit from PCM to valve is OK, PCM can activate it when commanded, and no "Evap circuit fault" code. I would suspect a logic problem in the PCM, or maybe a programming concern. Any TSBs/service bulletins from Nissan for this concern?

Wish I could help. Best of luck figuring it out.