Just want to share with you guys my experience today with regard to this issue which seems common among Lexus 3UZ-FE equipped vehicles. When you have the P0440 code appear, it could be most likely the gas cap. But how do you know for sure. Open the gas cap and inspect the rubber O-ring. Make sure there's no gap, break, or cut, it should be one complete ring. I had no idea before what to else to do when people say "leaking gas cap". I simply try to tighten the cap but that's not enough with a bad rubber o-ring. Chances are it is the cuprit.

I'm grateful I went to my trusted mechanics. I've been going to Dynamic Auto Services in Fountain Valley, CA (they used to be located in Midway City) for many many years and they're simply the best! I drive 40 miles and pass hundreds of Toyota/Lexus shops on the way whenever I need someone to fix our Lexus vehicles. No hanky-panky in the way they diagnose and fix your car. Just straight, up-front, and friendly assessment of what's wrong with your car. I have referred many happy relatives and friends to them. Folks from ClubLexus forum go there. Today, I went there because my Check Engine light was lit on my Lexus SC430. Norman hooked up the car quickly to a code scanner and found that it has an issue with Evaporative Emission Control system. Norman was quick to explain that it could only be one of two things-- the Gas Cap seal, or the sensor in the fuel tank, or both. No wild guessing or fake troubleshooting or need-to-overhaul-the engine scheme LOL. He suggested to first replace the Gas Cap with a new one because the substantially expensive sensor replacement job in the gas tank may not even be the culprit. He replaced the gas cap and cleared the Check Engine light, tested it, and told me to drive it to confirm it is fixed. Son processed the bill and explained the problem further. Bill: $54.75! (parts, labor and tax)

Son was an 11-year Master Mechanic with Longo Lexus before he opened the shop and that tells you a LOT! He said that he makes less money as shop owner but that he is now able to take his time and do a better job and lead a much less stressful life. As suggested, I drove the car another 50 miles, the Check Engine light never returned, and I headed to the smog check shop for DMV renewal. The car passed the smog check! I'm writing this so that people experience the delightful feeling of not having to worry about car repairs and all the bad examples we've all heard before. There are still great, honest, highly-skilled and friendly mechanics out there who don't charge an arm and a leg and Dynamic Auto Services is at the top of the heap! Let's support this business because I'd like this shop to still be around years from now if and when our reliable Lexus/Toyota vehicles need some fixing.

 

Thanks for sharing. A bad gas cap seal throws a code in many modern vehicles. Im glad you get great service.

 

Excellent tip, thanks! While my SC430 never had a problem with the gas cap or threw a CEL, I just replaced it. Figured it was 12 years old and was removed and replaced many times to allow over six thousand gallons of gas go by...

 

Nothing beats like a trusted mechanic. For all of us who really understand this statement, you can take it to the bank!

 

Well it was my turn! I had the P0440 code and I reset it on two different occasions recently only to have come back again.
below are pics of the new and old caps. I paid $20.35 for a new Toyota cap, Amazon. Ordered Friday and arrived while I was at church.

note the crack in the old cap gasket



.

 

It's nice when it turns out to be an easy repair, eh Bgw?

 

well I certainly hope so, ;-)
will know in a day or too.

 

I too had this code and replaced the gas cap which worked for awhile. Got the code again after several months. This time I bought a $5 tube of stuff I placed around the edge of the gas tank rim and have not seen the code since. SC430 has 180K miles.