SOLVED: Check engine light, P0456 code, gas cap loose

[themechanic]

Mom's 2007 Chrysler 300 3.5L V6 has the check engine light on for years. The error message on the dash says check the gas cap. The cap had been replaced more than once. I searched the interwebs and discovered it's a very common problem with Dodge, Chrysler, Jeep vehicles and is caused by a leaky Fuel Vapor Leak Detection Pump.

It seems the seal goes bad or begin to leak where the wire connector meets the main body of the pump on the ones without a seal.



https://www.autozone.com/engine-man...-vapor-leak-detection-pump-esm1001/125190_0_0

 

[themechanic]

This might be too much detail for those who just want to know what caused the problem. If so, skip to the end. For the rest of us car nuts the video is exactly what we want to know.

 

[Mopars & Missiles]

Thanks for this info. I've got a 2009 Jeep Grand Cherokee with this same leak code. I've pretty much narrowed it down to this same area (the charcoal canister assembly) but as of yet had not been able to pinpoint the leak as this man did with his "smoke machine". After watching the video, I'm pretty certain that this applies to my Jeep and will fix this code problem for me as well.

 

[65-440]

The problem with those ESIM's is that they fail open, causing the tank to vent full time creating a "large" evap leak. The same as if the cap was off, that's why you get the check cap message. The older NVLD pumps you could actuate and determine failure, not with the ESIM.... you pretty much have to block the vent hose and make sure there are no leaks in the system. If the system holds pressure then replace the ESIM.... and make sure you replace the seal at the same time!

 

[themechanic]

The problem with those ESIM's is that they fail open, causing the tank to vent full time creating a "large" evap leak. The same as if the cap was off, that's why you get the check cap message. The older NVLD pumps you could actuate and determine failure, not with the ESIM.... you pretty much have to block the vent hose and make sure there are no leaks in the system. If the system holds pressure then replace the ESIM.... and make sure you replace the seal at the same time!

Some, like the 07 Chrysler 300, don't need the seal.

 

[themechanic]

I stopped by AutoZone and bought 1 of 2 possible part numbers, ESM1001. I pulled the passenger side rear tire and plastic wheel housing only to find I needed the other part number, ESM1002. Just my luck.

The difference between the 2 is how the hose attaches.

AutoZone happened to have those plastic body panels fasteners like the ones that I destroyed pulling the wheel housing off. But there are 3 different types of plastic fasteners and a sheet metal screw. I should have gone by the dealership for the correct fasteners. But the ones I bought worked fine.

No more evap system leak, error codes or gas cap messages.