CEL Purgatory
 

Brief background: We bought a 2007 HHR used back in 2011 and it's been my son's daily driver.

In December, the CEL came on and he got a code read at autozone - P0442. Retightened the gas cap and gave it few days. Light stayed on so we tried a new gas cap from the auto parts store and reset it. Light came on in a few days. Mid-January we bought a GM gas cap at the dealer and reset the light. It came back on in a few days. Same code every time.

So we finally took it to the dealer for diagnostics. They called after a couple hours and said it was the gas cap. I told them it was a new cap we bought the week before at their dealership. They figured it must have been defective and put on a new one. They had to clean up the mating surface, but they got it sealed and smoke tested and pulled it out front and parked it while we paid.

My son got in the car to drive home and it wouldn't start. Starter crank, but no fuel pump start. So they rolled it back in the shop and spent well over an hour trying to track it down and finally found that a ground wire for the fuel pump had been damaged and replaced it free. They thought it had probably been that way for a while, but just a fluke it happened then. So all was good and my son said it actually seemed to be driving better.

And you guessed it -- freaking light came on again within a week. It was the day after my son filled up, so he tightened the gas cap and gave it a few days to clear. Which it didn't and it was the same code AGAIN. So another trip to the dealer and it took them an entire day to track down that the vent solenoid wasn't holding under pressure and they kept it until the end of the next day to get it fixed. That was 2/18.

I got a text from my son that the freaking light is on AGAIN. He'll go get a code read but we presuming it's likely the same or very similar. Assuming it's the 442 again, any suggestions on easy things to try before taking it to the dealer AGAIN? They have been pretty gracious about keeping costs down, but I'm afraid at some point they may ban us from the property!!!

If we do try something, how long should it take to clear the light if it is the fix?

ETA: I'm not sure if it's relavent, but it's been unseasonably warm the past couple weeks -- in the mid-80's. A front came through and today is a bit cooler - high in mid-70's. Don't think that little bit of change would affect anything, but at this point I'm looking for any clues. I will talk to my son when he gets home and find out how much gas is in it, etc.

the code should clear when the battery negative cable is disconnected for 5 minutes or so. Try that if it returns inspect all the fuel vapor hoses from the engine all the way back to the fuel tank. most of the time you will find a split hose or one that is disconnected. the vapor hoses rarely leak fuel but some times you will get a fuel smell around the leak.

Follow this link. Gas cap is only the FIRST on the list.
http://www.obd-codes.com/p0442

My guess is one of the "purge" bits is bad, probably the solenoid. But could be something like the dipstick is not sealed in the tube. Small vac leaks are a "b" to track down.

Get your money back from the shop that did not do a complete diagnostic.

Which dipstick would affect the evap system? We have an appointment for Monday. I'll poke around and see if anything obvious or if I smell gas.

That was only an extreme possibility. There is only one dipstick.

The PCV/EVAP on these cars is a closed system The oil cap, the dipstick, the PCV hose, the evap solenoid, the evap vent valve, the gas cap are all interconnected.

Don't be paying for the shop to throw parts at the code. Pay for what fixes the problem. They will usually sell you the part at the top of the list, then work their way down; and you have to pay for the experiments. Maybe your shop is honest and good, I hope so.

I really hope they are honest as well. It's just hard to know unless you can sit there and watch what they do and know what they should be doing. How do you know if they did a reasonably complete diagnostic? It's impossible to replicate every combination of factors that affect the tests. They gave it a 17 mile test drive, cold and hot start and it was fine.

It's pretty hard to determine if they did a complete diagnosis - that's why it is good to develop a good relationship with the Service Writer, or Service Manager. Sometimes the diagnostics can be very time consuming, and there fore very costly. I imagine it is not an easy job for them to balance out "thinking they fixed it" vrs running all those costly diagnostics.

Unfortunately a lot of problems will only show up intermittently - like in your experience. The computer is sort of forgiving for some problems, and will log the problems, but only light up the Check Engine Light after a certain number of instances of the "problem" - and sometimes monitors over what they call "drive cycles". So a part can be replaced, and the error light reset, but the light pops up after a few days or a few miles, according to what the computer is monitoring for.

It's back at the dealer today. I hope they can find a definitive answer.

How difficult is it to replace the purge valve (under the hood), the evap canister, or the hoses involved? I want to have some idea for what is doable in the driveway vs. really needing a mechanic. I suspect the biggest challenge is just access.

Under hood is real easy after you puzzle out how to disconnect the tubes. The only help I can give is "gentle manipulation". They are available at Autozone for about $15. Check the part number thread for the part number.

ugh - it's 5:15 and no word from the dealer and I left a message over an hour ago. The place closes at 6 - it'd be nice to know what is going on!!!!