I agree. Several years ago I experienced code P0441 on my 2003 Neon. The NVLD assembly is located towards the rear bumper area and behind the right rear suspension arms. It is a plastic assembly attached to a metal bracket which is bolted to the vehicle sub frame. It has 2 hoses about 1/2 inch in diameter attached to it and a 3 wire electrical connector.
When you shut down the engine the evaporative system is sealed. Due to natural cooling a slight vacuum will occur in the fuel tank and this is sensed by the NVLD assembly. When about 1 inch of vacuum develops in the system (assuming everything is sealed and no leaking hoses) the NVLD switch will close and a low voltage electrical signal is sent to the PCM (powertrain control module). If the PCM sees this signal within a predetermined time period, it assumes the system is sealed and is working properly. If the PCM does not see this signal within a set time period, a diagnostic code P0441 is set and the check engine lamp illuminated.
Check the hoses at the NVLD assembly. One is a friction fit and the other has a plastic clamp. If the hoses look good then the switch is not closing properly and passing a low voltage when it closes. It is possible to check this NVLD switch.
Carefully remove the 2 evaporative hoses (about 1/2 inch in diameter) from the NVLD. Remove the 3 wire electrical connector and note which pins on the NVLD are associated with the ground (black wire) and switch signal (red wire). The red wire and pin is the center terminal. Remove the NVLD from the vehicle.
Plug one of the 1/2 inch ports on the NVLD so it is leak free. Attach a hand held vacuum pump to the other port. With no vacuum on the system use a volt-ohm meter and check for continuity between the black wire terminal and red wire terminal noted in previous paragraph. The circuit should be open / no continuity.
Now apply about 1 - 2 inches of vacuum to the NVLD port. The volt- ohm meter should now indicate a closed circuit and continuity between black wire terminal and red wire terminal. If no continuity appears then the switch is not functioning properly.
I tried to open the NVLD and gain access to the switch but I *******ly destroyed it in the process so I had to purchase a replacement anyway. I believe corrosion and carbon builds up on the NVLD contact points and then after a period of time / years it will no longer pass current. Or it is possible the internal diaphragm develops a leak and will not allow the switch to close. I believe the NVLD assembly was in the price range of $50 - $60.