Hi. I've got a 2001 Monte Carlo LS with the Check Engine lit, spitting out a code of P0440 (I've got my own OBDII scanner). It has been lit since I bought the car and everytime I clear the code, it comes back at least two days later, or the first highway trip the car takes. Even when the code is erased, the emissions status on the scanner is still showing yellow, which is mid-range. I've determined that the purge solenoid and the fuel pressure sensor on the sending unit are not the cause of the code by switching them out with known working good parts. My next step is to check the vent valve and lines running to the canister and vent valve. Where exactly is the vent valve located on the fuel tank? Is it accessible by removing the access panel in the front part of the trunk (this lets you access the sending unit on top of the tank without lowering it). I dont't remember seeing anything similar to a valve when I replaced the pressure sensor. Or would I need to lower the fuel tank to get at it? I thought I read in an internet forum that access was gained by removing one of the rear wheel inner fenders, but I don't recall which side of the car. A clear answer to this would be very helpful, and possibly save me a lot of extra work.
Any help to locate this part would be greatly appreciated. Also, I'm looking for a part number for the vent valve, I'm having trouble finding one on any internet parts store.
Thanks, Sharky