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EVAP code p0446 HELP

Brad OSullivan

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Brad OSullivan Enthusiast

Brad OSullivan

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Hello guys, this has probably come up a million times but my 2005 silverado 1500 with the 5.3L has a p0446 EVAP code. Its for a vent control circuit malfunction. I have done a ton of research and have replaced a few parts so far including the vent valve, fuel cap, and fuel tank pressure sensor. WHAT else can it be!! The only symptoms I notice that could be a clue is every now and then when I begin fuelling, the pump stops like 4 or 5 times and then pumps steady to fill up. Could this be a sign of a bad canister? I'm not sure if anyone has any idea let me know, I got to pass emissions in February. Thanks!

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    • Atlas
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    • Chuck FB
      Tire pressure for 37s

      By Chuck FB · Posted

      First off you mentioned "Toyo Says" and then gave the pressures 45/50, was this some person at the tire shop that pulled those numbers out of his head ?   Now of course I can't know your exact axle weights front and rear, however I have much the same pickup as yourself other than not knowing your starting weight as per the pounds the truck rolled out of the factory at due to the options yours did or didn't come with or what you have added beyond the extra tire weight. The correct way to know 100% where a person is at is by weighing each axle with the typical weight the vehicle is driven with and that means taking into account passengers and making sure you figure in a full tank of fuel and a little grace for whatever you may put in the bed "groceries" !    I am looking at and not that it really matters as all the tire companies use the same charts anyway, but I am looking at the comprehensive Toyo tire chart in the section that your tire falls under and I know it sounds confusing but your tire is not an LT metric tire like your factory tire but instead because its a standard inch measured tire its under a different category called an LT floatation series tire. That makes a difference as LT metric tires they don't want to see run below 35 psi at highway speed where as with the LT floatation series it can be run down to 25 psi on the highway as long as the weight on the said size of tire is agreeable with or less than that minimum 25 psi. It blows many people away that how is this physically possible, an empty truck for one thing and larger tires with the same size wheel diameter have a lot more air volume so they can carry the same weight as the smaller tire with less air pressure.    So my truck, I have the stock 275/65R20 wheels and tires and I have a bit of weight in the box with a bak flip cover and a rubber bed mat and some tools and spare gas. The front of my gas truck weighs a bit more than some trucks of the similar spec due to double batteries and alternators. However with full fuel and just me in the truck I am weighted such that I can run 40 front and 35 rear and so that is what I have done since day one.    If I base your truck at or slightly below the weight of my truck, in theory with your tires going by the tire chart you might be right around a minimum of 30 pounds front and 25 pounds rear. Of course that would hit pretty much minimum cold inflation pressure one could run with that tire size and a near empty truck. If you have access to an accurate weigh scale to do individual front and rear axle weights I would suggest you do that and make sure your topped up with fuel and whatever else in the truck before you weigh it and then you will have a great starting point to work off of and figure out what your bare minimum pressures are you can safely run. If you do much in the way of hot weather high speed driving, bumping up a bit for a safety margin is never a bad idea but just depends on what type of driving you do. I will include the Toyo chart and the floatation series sizes start on page 31. Without a doubt at these pressures I am speculating at minimum wise for your truck, it would most certainly ride very different then it did when you were using 55 lb front and rear.     https://www.toyotires.com/media/pxcjubjs/application_of_load_inflation_tables_20200723.pdf
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    • PBNB
      Tire pressure for 37s

      By PBNB · Posted

      How wide are your rims?   Toyo specs 8.5-10.0-11.0 inches. My thought would be rim might be pulling the tire inwards creating a center that is more pronounced.    I also noticed that the spec sheet says max 65psi. So you could be right lowering the pressure to ~40 psi. 

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