I have had this code pop up about 4 times over the past 4 or 5 months, ive researched what to look for but curious as to if anyone else has had this same code pull up and what the solution was. Thanks in advance!

Yes, I've had this code before and my gas cap was not fully secured.

I see you've had the problem for a few months so I'm sure you've probably had time to tighten the cap, but I still check to make sure your cap is making a complete seal.

http://nissanhelp.com/diy/obd_codes/p0456_nissan.html

If it is not your gas gap causing the code to pop up you will need to replace your Vent Control Valve which is located at behind the Right Rear tire in the rear bumper area.

A few days ago when starting my car I received a warning that my gas cap was loose. I re-tightened it, restarted the car and turned off the warning. Everything was good until about 3 or 4 days later when my engine light came on. I checked this with an inexpensive obd2 reader and it gave a po 456 code.... Evaporative emission control system leak (small) Since I inspected and tightened the cap the loose cap warning did not come back on. Would there be any point in eliminating the check engine light and see if it returns.

The ECM can't re-test the fuel tank immediately when you have a loose cap, it needs to wait for the right conditions and run the EONV test while the car is parked for at least an hour or so. That's why you'll most often get a loose-cap code when you first start the car overnight or after work. If it isn't the cap, the most likely cause will be either a leaky Evap Vent Valve or a leaky o-ring for the valve.

Well I suppose I should try a new gas cap first and if that does not work change the evap vent valve. Afterwards do you recommend driving to remove the check engine light or is it better to use the scan tool instead?

drummerguy wrote: ↑

Wed Aug 31, 2022 8:37 pm

Well I suppose I should try a new gas cap first and if that does not work change the evap vent valve. Afterwards do you recommend driving to remove the check engine light or is it better to use the scan tool instead?

Definitely a scanner. Once an evap code goes "past", the ECM needs to run two more consecutive EONV's before it will turn off the MIL. So you're into at least three drive-and-park cycles, and perhaps much more if conditions aren't right. It helps if you maintain between 1/4 to 3/4 in the fuel tank while checking to see if the leak is gone, EONV won't occur if it's above or below that.

ok thanks VStar