Check Engine Light

[jtstacy77]

Had a check fuel cap message on my DIC. Checked the cap and everything was OK. Now I have a check engine light but no check fuel cap message. Hit the onstar button and they told me to check fuel cap and wait a few days. Could my cap be bad or do they tell you that with any check engine light. Truck knocks some times so I wonder if it may be my spark knock sensor? I will get it checked at advance this week to get the code. Any other thoughts or ideas? Thanks for any help!

[oldschool327]

You need to clear the DTC and see if it happens again.

[RyanbabZ71]

I had the same thing on our 08 Tahoe a few yrs ago (actually with less than 2K miles). Onstar asked if I gotten gas recently which I didnt (was over a week). Took it in and it was a faulty cap. 1st thing the tech checked/asked was if I had gotten gas recently and if I tightened the cap. I just had to shake my head and remain calm.

[StoneCutter]

Had the same thing happen to me during the winter months. It was -33ºC up here and I had a check engine light. Came out - cold truck. Turns out the check engine condition locks out the car starter.

 

Anyway - OnStar told me that it requires three cold starts before the condition will clear itself (if it's a fuel cap seal issue). Three mornings later, the light went out and coincidently, it warmed up too.

[Doug_Scott]

I had the same thing on our 08 Tahoe a few yrs ago (actually with less than 2K miles). Onstar asked if I gotten gas recently which I didnt (was over a week). Took it in and it was a faulty cap. 1st thing the tech checked/asked was if I had gotten gas recently and if I tightened the cap. I just had to shake my head and remain calm.

 

You would be amazed at the number of people that do not put the gas cap back on properly. As with anything else, you always start with the easy part, and usually you are done after that.

[OKLAGMCRUISER]

did they atleast tell you the code that was thrown? P0440? I think...is leak in evap system...most of the time due to a faulty gas cap or improperly installed one. Can be other things though, but as stated...easiest solution to start with.

 

Pat

[jtstacy77]

did they atleast tell you the code that was thrown? P0440? I think...is leak in evap system...most of the time due to a faulty gas cap or improperly installed one. Can be other things though, but as stated...easiest solution to start with.

 

Pat

 

No they didn't give me the code, but I will get it checked at the local Advance Auto this week. Do I need to replace with a gm cap or is an aftermarket OK?

[Bob D]

Aftermarket is fine.

[jtstacy77]

The code is p0445, just as you guys suspected. Do the seals on the gas caps really go bad? I've owned an 01 sierra, 02 sierra, 04 silverado and now 06 avalanche, never had this issue until now. Is there any way to check the cap or should I just replace it first? Also where is the Evap Vent Solenoid located? Thanks again!

[RyanbabZ71]

The dealer had some device to check mine for leaks. They are cheap enough replace it clear code and see if it is fixed, mine was under warranty so I took it in

[jtstacy77]

The dealer had some device to check mine for leaks. They are cheap enough replace it clear code and see if it is fixed, mine was under warranty so I took it in

Thanks, I will get a new one this weekend and clear the code.

[OKLAGMCRUISER]

on my 99 sierra i had this issue and i replaced the cap with a locking cap from a denali..around $25 from the dealer.

[jtstacy77]

Put on a new stant gas cap 1.5 weeks ago, and happy to say the CEL went out this AM! Thanks for the info.

[jtstacy77]

The CEL and tighten gas cap code are back for a week now. Guess it may be the evap vent solenoid. Is it the one under the plastic cover on the motor or the one located to the side of the spare tire. If it is the one next to the spare how do you remove that thing?