Whats up with my Check Engine light?

A couple of months ago I took my car into my garage to find out why my check engine light was on. They told me I needed a new gas cap. I went to the Chevy dealership and bought a new one. A few days after the check engine light came back on. I went back to my garage and they said I needed a canister vent control valve. I had a new one installed and again you guessed it, the check engine light came back on. This time I was told I needed to have a valve purge under the hood done, so I had that done. Once again a few days passed and the check engine light came on. At this point my garage was out of ideas. They told me they could only go according to the codes that were coming up on their computer as to what was wrong with my car. They suggested I go to the Chevy dealership and see what they say. Anybody have any ideas whats up with my check engine light?

There is a leak somewhere in your vapor recovery system, the fuel tank venting system. If you don’t need to pass an emissions test you can ignore it. If you must pass such a test, you can spend a lot of money tracking problems like this down…

maybe a “smoke” test could be done. the only problem with not fixing it is when something else goes wrong you will still think it is the vapor system.

What you need is not a new car part, but a new mechanic.

Just for the fun of it, you might tell us how many miles you have on your Malibu, how long you have had it and if you have had any other problems that may have had. The other thing that might help (although I believe everyone has guessed correctly) what was the actual error code. It will be in the format [P1234].

My husband and I have had the same exact problem with our 2000 Oldsmobile Alero since the summer before last, when our “check engine emissions” light first came on (sustained, not blinking, and the engine runs fine even though the light is 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.

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 in about a year ago to fix another problem with the blower motor resistor, and they too found that the vent valve solenoid was sticking, so they replaced it.

When we took it to the local GM Service Center in July of 2009, 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 our local mechanic, who did a smoke test but couldn’t detect a leak. I asked him if it could be an electrical problem. 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.

When I took it the the local mechanic, 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.”

When I was visiting my family in August (about a 900-mile drive there), the left-front wheel hub assembly needed to be replaced. They too checked this out but couldn’t determine why it was happening, so they reset the code. The check engine light stayed off for the entire trip back, but then after a while, predictably enough, it came back on. The car continues to run fine, and so we’ve given up hope of finding an answer.

The best assessment anyone can give us is that there’s a slight emissions leak somewhere, but the smoke tests aren’t pinpointing where.

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 last year.

Actually I had a smoke test done and they couldn’t find any kind of leak. Come the beginning of next year when it’s time to renew my plates I will need to pass an emissions test. I am hoping to find an answer before then.

I have 110000 on my car. I have had no other problems other then the usual upkeep one does to a car. I don’t have the error codes on hand, but I can tell you that all three times my check engine light came on a different code came up for each incident. I happen to trust my mechanic and truly believe they are at wits end as to what is actually the problem.

I am curious what checking your electrical has to do with the check engine light. I have been having issues with my blinkers staying on once in a while when I use them. The blinker will not actually blink after turning a corner and it shuts off but the sound will continue. If you can understand what I just said. LOL That has been going on for about 6 months now. Is that something I should have the garage check for?

I agree with Mr. Meehan, you need a new mechanic. If they replaced all of those items THEN told you to go off the CEL codes, they seriously need to fix themselves instead of cars. From the way you word the first post, they haven’t even READ the codes yet to find out what’s wrong with it.

Re: electrical, the reason I asked is because when I originally posted my questions about this situation here on the “Car Talk” forums, another poster suggested that I ask our mechanic about whether the electrical system had been checked, so I did.

I would say yes, have your garage check to find out why your turn signals aren’t working because after all, it’s a safety issue. You’re alerting other drivers to the fact that you’re turning.

Actually, I read it as they took the codes as gospel. Which is just about as bad. Codes lead you in a general direction, you need to do actual diagnosis to find the problem.

I can’t speak for the check engine light, but I had the same problem with the multifunction switch (turn signal, cruise, wipers, etc) on my 2000 Blazer. The turn signal worked normally, but the sound (clicking) was continuous.

I did some research and it was a fairly common problem with late 90s/early 2000s GM vehicles. I replaced the multifunction switch myself, the cost was ~$200 for the part. Figure 2 or 3 hours of labor for the job. By the way, this should not set a code

Try this first, spray some CRC Electrical Contact Cleaner into the base of the switch at the steering column to clean the contacts while working the turn signals. This worked for a few days with my Blazer, but I still ended up replacing the switch. Perhaps you will be luckier.

Ed B.