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Skyvisions, ASE Certified Technician
Category: Lexus
Satisfied Customers: 14324
Experience:  Lexus Expert
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2002 Lexus Ls430: Check engine Light..P0440, P0441..air box..gas cap

Customer Question

Check engine Light on with three codes P0440, P0441, P0446 on my neighbors 2002 Lexus Ls430. I did a little research and found that a valve near the air box may have been a likely culprit which I replaced (part# XXXXX). The light was reset and the gas cap checked for tightness. He was able to drive for over 100 miles before the light reappeared with the same codes. Any suggestions on what else should be checked before I start blindly suggesting unnecessary parts?
Submitted: 5 years ago.
Category: Lexus
Expert:  Skyvisions replied 5 years ago.

Thank you for choosing JustAnswer and allowing me to help you resolve your Lexus questions!


Whenever you have the P0440 code combined with the 441 and 446 the later 2 codes are usually false codes due to the evap system not being able to hold the correct pressures. The P0440 code is a leak in the evap system. Without a evap pressure tester/smoke generator it is difficult to find these leaks. If you live in a high corrosion area it is possible that the tank bypass VSV on the charcoal canister could set these codes or an internal leak in the canister can also do this.



Customer: replied 5 years ago.
Thank you. I guess I won't be able to fix it right by myself without a pressure tester or smoke generator. I was afraid of that. I live inland in the Los Angeles area, so corrosion factor would be low. I would be more than happy to pay the fee with a bonus if the answer led to getting it fixed myself. Gotta save some dough to get it professionally tested. Hope you understand. Thanks again.
Expert:  Skyvisions replied 5 years ago.

It is very difficult to do diagnostics on these evap systems without the proper equipment. I do not like recommending parts replacement to solve a problem either. The good thing is that corrosion or rusted out filler neck and lines can probably be ruled out. However check the filler neck for pitted surfaces where the gas cap seals onto the filler neck. Also replace the gas cap with a Toyota or Lexus gas cap not a cheap walmart cap. These are the quick things and cheap things to try first. Let me know how the filler neck looks.



Customer: replied 5 years ago.
Filler neck looks good.
Expert:  Skyvisions replied 5 years ago.

Have you tried the gas cap yet and are all the hoses connected? Did the car have any recent work done?



Customer: replied 5 years ago.
Had the gas cap tested at a smog place, tested good. Oil change recently, but neighbor says the light had been on for over a year and only now needs to have it checked out as he needs to have a smog inspection. I took the car into a place that has a smoke tester. I'll let you know what they find as soon as I find out.
Expert:  Skyvisions replied 5 years ago.

If there are no external leaks you are probably looking at the canister assembly. The VSV on the canister is know to go bad also but normally does not set the 440 unless the canister leaks internally. I have seen some of the diaphragms leak.




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