New to me 2002 ES300, I had a shop pull the fuel tank and replace the rollover protection valve and all the gasket/O-rings on the fuel tank. The valve was leaking it smelled like gas really bad by the rear of the car. Afterwards no CEL.
I went to fill it up after the first full tank of fuel and I really had a hard time getting the gas cap off. I thought I was going to have to destroy it to get it off. After I took it off, it went on and off easily. The cap is new ish. I do not think it is a Lexus/Toyota part. I am planning on picking up a OEM one tomorrow at a Toyota dealer.
Could it be something like the cap is not a vented cap but should be? Is that why it was stuck? The CEL came back on after that first fill up. Lots of emissions codes. I cleared them and it seems fine so far.

 

I don't think vented gas caps have been a thing for 50 years. Get a new one from a Toyota dealer and your codes will probably go away.

 

Thanks for info

 

Well I picked up the new OEM Toyota gas cap and installed it yesterday. It looked exactly like the one I took off that I was not sure was OEM or not. This morning otw to work the stupid CEL came on again. I have not been able to scan it yet. Ugh!

I had some work done on the evap system under the engine cover when I had the fuel tank repaired. There was what appeared to be a small rectangular check valve under the cover. It was cracked beyond repair. I was not able to find that part anywhere, even Lexus. The entire assembly had a part number for the check valve and 2 solenoids. It was over $1200 from Lexus and was unavailable. I pulled one out of a junk yard that was similar. The part has no electronics. It appears to only be a vacuum check valve. I think my original was for 2002 only. The car I got the similar one off of was a 2005 I think. I am wondering if that check valve is installed backwards? That would possibly explain the significant vacuum on the fuel tank preventing the fuel cap to be removed. Any ideas on what this part could be and maybe a diagram of how that system works?

 

was it the plastic rectangular box with two fittings on it being pointed to in the picture?

If so, it is not check valved. You can blow through either end

 

Hello,

Yeah, it's just a Surge Tank for when you open the throttle abruptly, here is a thread about it, I doubt it's the cause of your issue.

Pull the codes you have, some of them may not even end up being related to EVAP system. Also, you mentioned there was work done on the Fuel Tank, what kind of work was it, and did anyone verify that it is sealed?

Hope this helps and best of luck!

 

Yes that is the little plastic box. My original 2002 model crumbled to pieces. I got one that was close off a 2005, I think, from a junk yard. It was the closest thing I could find. That vacuum diagram routing pic is exactly what I needed. Thanks. I actually pulled it all apart yesterday. The "fix" that was done by the shop was "iffy" at best. They warned me it may not last. When I pulled the cover off yesterday one of the hoses had popped off. It was kinda a mess. I re did the hoses with some stuff I had. I routed it just like your diagram. I just happened to get lucky I guess. So that box is not a one way valve of any kind? I did not try and blow through it. When I put it all back together and went to read the codes they were all gone and the CEL was off. Kinda weird. As long as the in and out of that box does not matter I should be good. I hope. I drove almost 50 miles to work this morning and no CEL so far. Time will tell. Thanks mucho for the help.

As far as the fuel tank. I had it pulled by a shop because it smelled like gas by the back of the car, really bad. It honestly made me a bit nervous to drive it. It was that bad. The rollover protection valve was cracked which is apparently a common failure point. The OEM one I bought was supposedly a updated part. I also had them replace all of the other gaskets/grommets while the tank was out. The fuel pump O-ring and 2 other vents on the tank. The grommets were in pretty bad shape when they changed them. Dry and cracked. No more gas smell back there now.

 

Well unfortunately the stupid CEL came back on the other day. Again.... Codes now are saying P0420, P0441 and P0446. It was talking about the vapror pressure purge vent? Where is that located? The P0420 is related to cat. I really hope it is not that. Thanks for help.
.

 

Check VSV in red
with no electrical current, you can blow through it - valve is open
with battery voltage applied, you can't blow through it - valve is closed

ensure vacuum hose is not cracked and connected properly

as for P0420 - checking live data bank 1, sensor 2 (downstream), reading should be more consistent state, not fluctuation rapidly . Rapid reading means CAT is not effectively cleaning exhaust gases