jdsaengine

Well, thought had the check engine light issue fixed by replacing the gas cap. Cleared all the codes and was good for about 3-4 engine start cycles.

Now check engine light is back with new code P0442 - Evaporative emission system small leak detected, PCM engine controls.

got this code after a short trip and before I shut the engine off. With a new gas cap, what would the next thing be to look at ???

mrlmd

Is that code H or C?
You said you cleared the code after you replaced the gas cap. You put the gas cap on tight, it clicked and all that? Have you checked it to see if it's loose?
Did you get a genuine GM OEM Corvette cap? When I just replaced mine, the dealer gave me a cap that fit fine, but it was made in Germany. I haven't had any problems with the light coming back on in 2 months and 1500 miles of driving since the new cap.

jdsaengine

Yep, the cap came from GM dealer in a GM plastic bag, but I have no clue where it was made. It had the same model number as the one sold by Gene Gulley, so I guess it was for the vetter, rather than a Malibu or something.

Clicked it good, several times. The code came back as C then HC. I've cleared all the codes again, but the light is now staying on all the time. last time at least the light went out for 3-4 starts.

midnight01

I had the same problem even with a new gas cap. I fixed it by looking at the cap and not making it click when I turn it. I look at the cap and the way it goes on the filler and only turn it about 1/2 inch and it is snug. After doing that I only see the CEL if I forget to follow my own instructions and tighten it til I hear it click.

jdsaengine

thanks, I'll try that. Last thing I want to do is take it to a dealer and give them a green light to charge $1000 to chase a small emissions leak around the entire car.

I'm also going to do the carb cleaner and WD-40 in the air pump hose/check valve trick even though the code is not related, anything to get rid of the CEL. Things like that just bug the H out of me to look at !!

Bill Curlee

Look on the drivers side of the engine. There is a vacuum nipple just rearward of the throttle body/manifold neck. There's a plastic fitting that has a hard plastic line that goes to a electronic solenoid after the solenoid is a plastic corrugated hose.

Those hoses have a tendency to crack and or break. That's the vacuum line and solenoid for the Fuel Tank EVAPORATIVE CANISTER System.

If that hose of pipe has a vacuum leak it will throw the same DTCs.

You can see the plastic corrugated hose on the drivers side at the rear of the engine:




Better picture of the hose:

jdsaengine

Well I checked the fitting/line mentioned by Bill C and it "looks" Ok. However, not sure how a positive check of a vac line can be done other than visually. Not like you can spray soapy liquid on it and check for a leak like tire leak

On a positive note, I did do the gas cap trick of attaching it, rotating about 1/2", but not waiting for the clicks. The wife then went out for some errands and she said the CEL went out. Its now been out for 3-4 cold starts so. . . . we shall see.

mrlmd

Get a new gas cap - that one doesn't fit correctly making a tight seal when the cap is put on properly. By not clicking it on, you are risking having it come off while you are driving.

midnight01

Sweet. I bought a new cap straight from GM and my issue came back again. I then did my little no click trick and it turned off.

midnight01

if he turns it a half turn there should be no way it comes off, unless the rubber seal itself is broken or no good. I bought a new cap to replace the one I thought was not sealing and it had the same issue, brand new GM cap I overpaid for lol. It might be my filler neck so when i get a chance I am going to smooth it out a little.

jdsaengine

I made sure the filler neck was clean and doing the 1/2" turn without clicking is still working. We just came back from 4 day trip, about 400 mi. and never saw the CEL so must be something to the "don't over click" a new cap method.

73Corvette

thanks for the update and hope you have many more trips...

jimmymac25

There is a huge difference between a 1\2" turn, and half a turn. Can someone clear this up?

midnight01

Turn it about halfway maybe less, if it clicks you turned it too far.

SRTZ06$

actually insane how many problems this car has im on my 4th week with the car and im about to sell it. I had 0 problems with my SRT it seems the more i bring the car in to service the more things go wrong

helga203

if I wasn't mechanicaly inclined this car would have been burned 15yrs ago

feeder82

so why get rid of a srt for a 20yr old car?

helga203

Looks better.

SRTZ06$

my c7 z06 isnt 20 years old. Maybe im in the wrong c platform but if so thats even more of a let down for chevy because my c7 had this same problem 😂