I buy/fix/sell/drive my fair share of Cavaliers, and I'll admit I've been just a parts changer when it comes to the P0455 code.... because that's all I've had to do. I keep a known good gas cap and vent valve handy to try out when "diagnosing" it. I've never had a car that a gas cap or vent valve hasn't fixed... until now.

This one is odd though. It has the problem where you cant fill it fast with gas, but it also has the P0455.. which to me is odd. If it has a large leak in the EVAP system I would think it would vent while filling fuel.

I've tried a known good gas cap, known good vent valve, known good purge solenoid and still have the code. Tonight I checked the hose between the charcoal canister and vent valve and its clear. I left the hose off the vent valve and ran to the gas station. It still was hard to get fuel in. I popped the hood and pulled the back fitting off the purge solenoid and it fueled the same.

I'm trying to really get an understanding of this system. The charcoal canister and the fuel pump assembly both look to have a vent line running to the front of the car. Where do both of those run? I would have to guess that one runs to the purge solenoid and the other goes to?

Has anyone ever actually found a faulty hose or line on an Eco Cavalier? Can a fuel tank pressure sensor be faulty? Even though these 2 problems seem to be opposites, could they be related?

Thanks for any input or ideas.


JLP

04 LS Sport Sedan

Did u check the filler neck and the hose at the end of it that goes to the gas tank for cracks or holes?

I agree with Jared, if there was something restricting the filler neck then the pressure would build up. I don't know what the ecotec filler necks look like, but I can tell you with the 95-02 cavaliers the filler neck had a small tube running right beside the filler neck from the tank all the way up to the cap. This is suppose to allow the air to escape when filling but still trap gas vapors when the cap is on. If either two lines were restricted you would have the issue of having to fill the tank slow.

As far as the P0455, your evap system shouldn't have anything to do with filling unless the vent solenoid was stuck open, maybe... When the car is off, the vent and purge solenoid should both be closed. But in the 95-02 you have a line going from the gas tank into the canister, then a vent solenoid to let fresh air into the canister, and then one line out of the canister into the purge. You also have a pressure sensor on the gas tank. If when the system is closed and the pressure was low or there was no pressure at all it would throw a light. So, when the torque convertor locked in, the vent solenoid would open letting fresh air in and the purge would open to burn the gas vapors.

As for the ecotec's I havent worked on them, but I have worked on a sebring that had two lines. One line went to the canister and purge and the other went to the egr vacuum solenoid I think... So when the egr would open the second evap line would be sucked into the manifold. idk its been a while.

For the p0455 code I would check the pressure sensor/ldp; if it was giving a false reading instead of no reading, then computer wouldn't know it wasn't working properly and it would say there was a leak. Also take the evap line off at one end of the car, plug it and hook and hand vacuum pump up to the other end. Make sure you exclude solenoids. If it holds vacuum without constantly pumping then there is no leak in the line.