Toyota Sienna Evaporative Canister (P0446) and SVS Valve Repair or Think Like a Maker

Update: The procedure described below did fix the problem and the repaired SVS valve lasted for about 18 months before the vehicle started throwing the same code. I replaced the SVS valve with the one listed below and the car has not thrown any codes for the past two years. If you have something other than a Sienna, click through to Amazon and look for similar valves designated "Dorman 911 vacuum valve." – Jake

Rage drove me to it.  Our 2001 Toyota Sienna failed it's Massachusetts emissions test this year, the problem was with the evaporative emissions control system (code #P0446) so I dropped it at the dealer to be fixed. 

You see, several years ago I decided I had  enough frustration working on cars and decided to focus on more fun pursuits.

Several things have happened since then.  #1- I have a much better shop and more capable tools.  No rusted nut or bolt can resist the hot wrench (mechanic's slang for an oxy/acetylene cutting torch) !  and #2 – I've become a radical Makepunk. 

. . .

So when the dealer called me with a quote of $720 my response was "$720 to replace a part that is essentially just a paint can full of charcoal! You got to be F'ing kidding me!"  Bastards!

So I got me a code reader from Scantool and did some research on common failures.

The most common failures seemed to be a saturated charcoal canister, a leaking canister, and the SVS purge valve solenoid.  The evaporative emissions charcoal canister in my 2001 Toyota Sienna is located under the plastic shield between the gas tank and the spare tire.

I unscrewed the shield and took a good picture of the hoses so I would have a guide when it can time to re-install.

There was no liquid gasoline in the system and only a slight smell of gas from the canister – it was clearly not saturated.  If it had been I was planning to drain it and then gently bake it in a very well ventilated area until dry.

Since one of the possible failures that would cause the ODB-II code P0446 the scan tool showed was a leaking charcoal canister I decide to pressure test it.  The local hardware store provided a selection of rubber stoppers to plug it's orifices and I blew into a tube until I could see the sides of the canister bulge – way more pressure then it would ever see in operation – no leaks.

I was going to disassemble and inspect the insides of these vacuum valves to make sure they were working but Toyota has glued the snap-tabs in place, the bastards! 

However blowing in to their various openings resulted in satisfying pops and appropriate resistance that made me fairly confident that they were not stuck or damaged.

This is the SVS Valve and it is suppose to be closed until energized, mine was stuck open.  I took a short trip to the local auto parts store but they had no such item.

There was no way I was going back to the dealer for the part so I decided to see if I could fix it.  It was pretty rusty but I was able to bend the tabs back and disassemble it.  The silver plunger on the right was indeed sticking in the barrel.  I cleaned everything thoroughly but is still stuck.  The next step was to take a piece of thin-wall brass tube that was a little larger than the bore and push it in.  That did  it, the plunger moved smoothly and when re-assembled the valve functioned flawlessly.  I suspected that the plastic in the valve body had swollen ever so slightly due to years of exposure to gasoline fumes.

The moral is; don't think like a mechanic who replaces assemblies, think like a Maker and seek the root case!

Everything went back in the car and I used the scan tool to clear the P0446 code.  The vehicle now needs to go through a few driving cycles before the ECU sets the 'readiness' code and it can be re-tested.  I did have to spend $98.95 for the scantool, but its time to start fixing my own cars again and they are mostly ODB-II so I needed a scanner anyway and its still a lot less then the $720 the dealer quoted.