Evaporative Emissions System (EVAP) Description

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Read About EVAP System Operation And Description

EVAP System Comments Page 2

1999 Ford Ranger. Can only fill the gas tank very, very slowly. Appears not to be venting. Where should I look to solve this.
 You either have something in the filler neck restricting the flow of gas, or a bad EVAP vent solenoid. Look down the filler with a flashlight, if it looks clear, then replace the solenoid.

1999 Pontiac Grand Am has code P0442 smal leak detected stored in the PCM. I have heard this could be a llose gas cap or a leak in the vent vlave or something like that. Can you give me some help please, thanks.
 Yes, P0442 is a small system leak. This could be cuased by a loose gas cap or a bad seal on it, but that will usually cause a check engine light code P0455 large EVAP leak. You can try to replace it and have the codes cleared to see if that repairs the problem. If not, you will have to see a mechanic to run a smoke test to find a small EVAP leak.

Is vacuum the only means by which the PCM will check the integrity of the EVAP system? Don't certain OEMs use pressure for the PCM to accomplish the same results?
 The PCM cannot create pressure in the system to run a test. It does look for pressure sometimes to determine if there is a problem in the EVAP system that normally only has inches of vacuum.


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2010 Chevy Malibu with mileage of 47,000. Took to the dealer with check engine light. No other symptoms at all, the car runs and drives normally. It returned codes of p2198 and p1440. Dealer says the canister purge valve and canister assembly are defective and need replaced to the tune of almost $700. I don't have that kind of money right now. First question, what are the risks of letting this go for a while until I get the money? Second question, is this legit, does it really need to be replaced at all? I don't have to worry about emissions testing in my area.
 If you do not have emission testing, then you can without these repairs.

I have a 97 Nissan Sentra gxe the EVAP vent valve is located near the gas tank behind the rear driver side reel right? I took it off and cleaned it and found the solenoid wouldn't activate when i plugged the wire harness back into it. Checked it with volt meter and was getting 11.5 volts. So i hooked it strait to battery which gave it 12.5 volts and the solenoid worked. i even blew into one of the hose openings to be sure no air was slipping thru when i did this. So i reinstalled it but cut the ground wire from the harness and rapped it around a screw now the vent valve is getting 12.5v. and activates soon as u turn the key. Seems to be ok but its getting really hot and i still cant clear the code and check engine light. And i got an emissions test coming up at the end of the month. Any suggestions would be greatly appreciated.
 What you just did by wrapping that wire around a screw was complete the ground circuit that the computer is suppose to control. So, the valve is on all the time. That is why it is getting hot. The engine light will still be on because the system is not venting when it is suppose to. Re-install the wires properly, test for 12 volts in, which you do have. Then test the other wire for the computer grounding it when it is suppose to. This would need to be done with a scanner to turn on the and off the valve. If no ground, check the wire back to the computer for continuity. If it OK, then maybe a bad control module.


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