2004 Chevy Silverado tighten gas cap

Tiny
DIANA.KRAMER@SBCGLOBAL.NE
  • MEMBER
  • 2004 CHEVROLET SILVERADO
Engine Mechanical problem
2004 Chevy Silverado Four Wheel Drive Automatic

Trouble code: P0455
Flashes tighten gas cap twice, then the engine light come on.
I've replace the gas cap twice with one after market and one factory. Checked all hose clamps - all seem to be tight and no holes in any of the hoses. I've checked the pipe where the gas cap seals and it's all nice and shiny with no gouges or dents.
This used to happen as soon as I had less than 3/4 of a tank of gas. Now it's happening sooner. Been dealing with this for about a year now.
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Tuesday, November 3rd, 2009 AT 7:58 AM

2 Replies

Tiny
OBXAUTOMEDIC
  • EXPERT
Hello,

Check for Vacuum Leak under the hood.

Since code def is.

P0455 Evaporative Emission Control System Leak Detected (gross leak)

80% of the time it is a Vacuum Hose in the engine compartment that has broken, come off, or is serverely cracked.

The other 20% is an intake manifold gasket has failed.

Mark S

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Tuesday, November 3rd, 2009 AT 6:17 PM
Tiny
KDRAKE1234
  • MEMBER
P0455 is a large leak detected if gas cap sealing surface is ok most likely cause is the evap vent valve it is a valve usually round located in front of the fuel tank or at rear. Electrical connection at valve rarely fails and all you can really do is inspect it visually its a red connector hooked right to the valve. With a tech 2 you can command the valve on and off and hear it click im fairly sure you dont have access to one so all you can do really is check the power supply to the valve you wont be able to check the control side that would be the ground. You could remove the valve and put power and ground to it and listen for a click but 99% of the time the vent valve is the cause at least in my experience. Gm replacement valves are of a new design you have to cut the plastic tube off the vent valve that goes to the evap cannister and hook it to the new valve with heater hose and clamps gm also wants you to run anther piece of hose off the vent valve to the top of the transmission with the provided filter clamped to the end.I dont believe this is completely necesary I usually just run them up the frame and zip tie them to the fuel lines right behind the abs module pump.
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Wednesday, November 11th, 2009 AT 7:24 PM

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