Hello everyone,
I’m new to this site and I need your help. I have a 2010 Nissan Maxima SV with 99,000 miles. I recently changed the spark plugs and replaced the valve covers because a tube seal was leaking on each valve cover. Car runs great, but now I have a PO455 code showing after driving it for 40 miles. Any ideas what could be wrong? I appreciate your input.

 

check your EVAP hose, a leak in the hose can cause it to shoot out "PO455" code. yes odd to check that even tho you did not touch nor change it but, you never know. not sure what could have caused it to give you the "PO455. not saying that what im saying is the issue it can or cant be, maybe someone will help you out more once they see the post.

 

A loose or missing gas cap will throw this code. The rubber seal on the gas cap might not be making contact with the filler neck. You could try a little white lithium grease on the rubber seal or change out the gas cap. Make sure you use OEM cap. You can clear that code by disconnecting the neg terminal on the battery for 30 minutes.

 

Thank you for your input. The car never gave me a code until I changed the spark plugs and the valve covers. I cleared the code and it came back after about 40 miles of driving again. I flipped the O ring on the gas cap even though it looked good. I will check the evap vent control valve for a cracked hose.

 

Are you sure you reconnected all of the vacuum lines after you put the manifold back on?

 

glad we can help, hopefully you get it figured out keep us posted

 

I double checked all my vacuum lines and the car does have a smooth idle. What I did notice is that when I double checked the gas cap there was no pressure or fumes when I removed it.

 

did you change the gasket on the plenum after you removed it to get to the spark plugs? Did you tighten everything to spec?

 

Yes I did. What I did find under further troubleshooting was that the hose going to the service port . Hose # 14912 MB had a big crack under the clamp. I cut the part that was cracked and found a copper bushing inside the hose which looks like it would restrict the flow, I removed the bushing. No idea what purpose it would serve. I reset the service engine soon light. Hopefully that solves the problem