2004 Chevy Silverado fuel cap

TEXASPEACEOFFICER

MEMBER
2004 CHEVROLET SILVERADO
V8
2WD
AUTOMATIC
80,000 MILES

My check engine light indicating my fuel cap needs tightening keeps coming on. I have replaced the old fuel cap with a new one, but when my tank has about 1/4 left, the check engine light comes on telling me my fuel cap needs tightening. How do I fix this?

3 Replies

SERVICE WRITER

MECHANIC
9,123 POSTS

The light is detecting a loss of fuel vapor, not necessarily the fuel cap. The code is po442 maybe?

This means that there may be leak elsewhere in the evaporative system such as a fuel filler neck for example.

Verify what code # is there and get back to me.

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Thursday, October 8th, 2009 AT 1:41 PM

TEXASPEACEOFFICER

MEMBER
2 POSTS

The code is po455

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Wednesday, October 14th, 2009 AT 10:06 AM

SERVICE WRITER

MECHANIC
9,123 POSTS

This is a large leak, and a vacuum can not be drawn on the evap system. Check the connections as per the drawing to make sure a hose is not off or damaged. A valve stuck open will also do this.

IF none, you can either have the system smoke tested or pull off the vent valve and check for any dirt inside of it. Replace if so.

Why so many different user names?
https://www.2carpros.com/forum/modcp.php?mode=ip&p=689171&t=357139&sid=e3bce73e7d2f32702cf386a99e09382d

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Wednesday, October 14th, 2009 AT 1:08 PM