My husband and I have had a problem with our 2000 Oldsmobile Alero since last summer, when our “check engine emissions” light came on. My husband first tried replacing the gas cap, but that didn’t fix it, so we took it to the local GM service center. They found that the vent solenoid was sticking, so they replaced it (or so they said).
Not long after that, the light came back on. This time, we took it to a local mechanic who did a scope and smoke test, but couldn’t find the problem. They reset the codes, and for a while the light stayed off, but then came back on again. I took the car back yesterday to fix another problem with the blower motor resistor, and they too found that the vent valve solenoid was sticking, so they replaced it.
Has anyone else had this experience and so can comment on why this keeps happening? Thanks!
What are the actual codes that are coming up? They are in a format like: P0123
Check your invoice, ask the mechanic, or many auto parts stores will read them for free. Find out and post the actual codes - there are hundreds of them including multiple codes associated with the evaporation system (which involves the gas cap and that solenoid).
When we took it to the GM Service Center in July, the code that came up was P0442. The invoice said, “Cause: Vent solenoid sticking. Correction: Replace vent solenoid, erase codes.”
The check engine light stayed off for a while, but then came back on. At that time, we took it to this local mechanic, who did a smoke test but couldn’t detect a leak.
When I took it the the local mechanic yesterday, the codes that came up were:
P0440 evap system fault
P0442 evap system small leak detected
That invoice says: “Smoke test, found vent valve solenoid stuck closed. Replaced vent valve solenoid, erased codes.”
A stuck vent valve could cause the P0440, but isn’t likely to give the P0442.
For the P0440, it is possible that you have gotten 2 bad purge solenoids off the shelf - though that is not very likely.
The solenoid will be electrically controlled. Has anyone actually checked the electricals? I.e. Is there voltage getting to the solenoid?
I also cannot say for certain, but my guess is that the engine’s computer is really only looking at vapor flow rather than the action of the valve. As such, the P0442 could come from a blockage in the evap system lines or even at the charcoal canister. I would first test the wiring for the solenoid to make sure it gets power. Then I would probably be pulling the vacuum lines both to and from the solenoid to check for blockage.
The smoke test may have only verified that no vapors are making it all the way through. If a blockage is found and cleared (rather than the valve being stuck closed) another smoke test may reveal some kind of a leak elsewhere.
Thanks for your input! I guess we’ll wait and see if the light comes back on again. (It never comes back on right away; usually it takes a week or so.) Also, I should note that the car runs fine; it’s not running roughly at all. The only indication of a problem is the “check engine emissions” light coming on.
As a side note, we have to have our car checked for emissions before we can renew our license plate. FWIW, our car passed that emissions test a month ago.
As far as I know, the electrical side of the equation hasn’t been investigated, just the physical emissions system via the smoke test. There’s nothing on the invoice from the GM service center indicating that the electrical system was checked, and I believe – though I am not absolutely certain – that the local mechanic was going only by the results of the smoke test.
If the light comes back on, then I guess it’s back to the mechanic for us!
Edit: I just spoke with the mechanic and basically read his reply back to you. He said they checked the electrical, and everything was working the way it should be. He pointed out that either current is going to the valve, or it’s not, and if it’s not, then the valve won’t work. They also checked to see that the pressure was increasing and decreasing the way it should (when you remove the gas cap off and so on). All of that was working the way it’s supposed to.
Just to update: We’re still at a point where the “check engine” light comes on and stays on (it’s sustained, not blinking), and no one can tell us why. This is after taking the car to three different mechanics (one GM Service Center in Canada, the other in the States and then our regular mechanic) to have it looked at. The best assessment anyone can give us is that there’s a slight emissions leak somewhere, but the smoke tests aren’t pinpointing where.