The xA, xB, Yaris and Corolla have TSB's out for water intrusion into the vapor canister. The xD should as well because it is a common problem. You will get the 5 OBD2 codes indicating vapor canister failure and you'll get lights on the dash, VSC, trac, check engine.
You will need to replace the vapor canister, which comes with a vacuum switching valve bolted to the end of it. The xD canisters are very expensive. The solution is to replace the canister with an xB unit, Standard/SMP CP429 which are about $225.00.
All you have to do is swap the metal mounting brackets from your old xD canister to the new xB canister. They are exactly the same otherwise IMO, im sure the stealership will tell you different.
There is a fix for the xB and xA which involves replacing the fuel filler hose/vent hose. All you can do with the xD is replace the canister and try to park it out of the weather
It will be obvious your canister is bad if you remove it and unbolt the valve from the end and shake it water droplets will come out. It will also be very heavy compared to a new unit.
Hope this saves people time and money. I think the xD canister is still expensive because they know there is no TSB or recall and the alternative is to get one from Toyota for $800.00. Toyota will also replace the charcoal filter if you have them do it.

I didn't replace mine but they are about $65.00. My xD is finally code free after replacement. I had previously tried to replace the gas cap and the 2nd vacuum switching valve in the engine compartment because they were the cheapest options for a possible fix.
It was still cheaper than having Toyota read the codes and provide a $1000 plus estimate.You can get the xB canister on Amazon and eBay.
If you are in California or have a California made car and you live in select states these parts may be covered by the Fed emission warranty. Do the research yourself before you buy any parts and don't believe anything a stealership tells you.

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sorry to bring this post back from the dead. I just want some clarity about what I should be doing. I got these codes on my dash driving home tonight. I JUST bought my xB 3 days ago. The night I bought it, I did "top off" the tank.. I had no idea this could happen, I always topped off my tanks in previous cars. So I bet that is the problem. I haven't had the codes read yet. But lets assume, that I'm right. Is the only thing that needs to be replaced is the evap canister? (77740-52100) ? Should I be replacing any other parts such as " Fuel Tank Filler Pipe Cover", "Charcoal Canister Assembly" "Charcoal Canister Filter No. 2" I haven't found the toyota service bulletin for my xb, but I did find one for the xA, and I believe we have the same parts. http://tijil.org/Scion_TSBs/eg04706.pdf I'm just so frustrated.

 

I've looked for this fix that hobojon talks about for my 06 xB and can't find anything that says "replacing the fuel filler hose/vent hose" or similar. Please point me in the right direction. Thanks.

 

Hobojon, can you tell me the year of your xD. I'm guessing 2nd Gen because the 1st Gen has the canister and valve separate and not 1 part. but please clarify.
Today I had Toyota look up the canister which includes the valve the part number is 77740-52090 and cost was $700.

Mine is a 2013 and this part is on eBay for about $150.

I'm going to do more research for the CDP429 xB canister and see if it is for their 2nd or 1st Gen.

Other tips I have learned in past few days messing around with my Evap codes. Can do a smoke test with a cheap cigar.
Can test purge solenoid with 12v wall charger (buy off eBay, 1amp is good). Test resistance with multi-meter of purge solenoid between 22ohm and 30ohm.

Large leak code usually is the canister not the purge solenoid under the hood.

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