Stranged Check Engine Light Question

[bigbengalbubba]

It seems my CEL comes on right around the time my gas tank gets to 1/4. Sometimes I can remove the gas cap and put it back on and it will go out. Other times not. When I put gas in it does go out until about 1/4 tank again.

 

Do I have a bad fitting gas cap? (possibly) or something else.

[J-man67]

I would say try a new gas cap. Might not be holding pressure as well as it once did so when it gets down to a 1/4 tank, when there is less volume that correct pressure isn't getting reached causing the CEL.

[redvett]

Get the code and then we can figure it out.

[rodram]

my suggstion is for a new gas cap... likely you are NOT maintaining the correct 'vacuum' in the fuel tank for the emissions control system...

[Chrisj]

I've been getting the check engine since new. i take it in and it goes out before I get there. This time it happened to store it on my diagnostic report. This is what I got on that.

 

Diagnostic Status: Complete. There may be an issue requiring action. Push your blue OnStar button and request a GM Goodwrench Remote Diagnostic.

 

This system is responsible for limiting the emissions from the vehicle, both by keeping fuel and its vapour contained in the fuel system, as well as by limiting exhaust tail pipe emissions by ensuring efficient engine operation.

 

NOTE: If your vehicle's Check Engine/Service Engine Soon light is on or not working properly your vehicle requires service and may not pass your province's emission inspection program (if one exists).

 

Evaporative Emissions System [+]

 

Evaporative Emissions System [—]

 

The purpose of the evaporative emissions system is to contain fuel vapours from the fuel tank and fuel system. When you fill up your fuel tank and tighten the fuel cap, the fuel system is sealed and the system ensures that any fuel vapours are used by the engine and kept out of the atmosphere. In the event that this system has a problem, sensors within the system can tell the engine computer to turn on the Check Engine/Service Engine Soon light, Check Gas Cap light, or another display message to indicate a malfunction. If the fuel cap is not properly tightened the system can detect this and also cause the Check Engine/Service Engine Soon light, Check Gas Cap light, or another display message to come on. It is important to ensure that you tighten the fuel cap after refueling. That information can also be sent to your OnStar Vehicle Diagnostic check to alert you that service may be needed.