P0441,P0455 Where to start

[SirLR]

I just got these codes come up ones a purge valve code for insufficient flow. Would the first step be to change the purge valve or the gas cap. Most people have changed gas cap and haven’t had any good results. It’s a 06 lx470 and I’ve seen a similar thread but the guy never updated. His techstream results were identical aswell.

 

[Malleus]

Have you tried the service manual?

 

[cbranch]

perhaps just replacing the purge valve may do it but fwiw a new pcv valve, hose, and grommet solved my p0441 code on the '00 lx. tried new oem gas cap but that did not work

 

[2001LC]

I'd make sure gas cap has good seal and on tight. Perhaps just replace gas cap, with OEM of year correct.
Clear Codes (DTC) see what if any return.

If DTC returns:
Look over engine vacuum hoses and wires. Make sure no vacuum leaks or wire unconnected or damaged.
Drop spare tire and look over Charcoal Canister (CC) above spare. For loose or damage wires/hoses or cracks in CC.
Clear DTC, see what if any return.

If DTC returns.
Test VSV (vacuum switching valve) on BK1 (driver side in LHD). Correct/replace if any issue.
Clear DTC, see what if any return.

Then very likely a new CC will be needed. When I replace CC on 06-07. I also replace 77706-60030 FILTER SUB-ASSY

Typically we see, one or more of other signs a CC bad:

• Engine running poorly, even stalling on hot day.
• Rancid fuel smell. Strongest around LH rear 1/4
• Gas cap area mucky (dirty) looking.
• CC weight over 89oz (new 2006-2007LC or LX). Clogged/bad CC, tend be ~110oz.

 

[SirLR]

I checked the gas cap and seemed tight and cleared codes already. I will end up checking the gas cap oring again and possibly replacing it. I found in the service manual how to diagnose so ill start with hoses and run the tests through techstream as well. I do not think its a fouled CC since I have no gas smell and engine runs great. I will diagnose and report back. The previous owner never changed the pcv so might as well do that aswell.

 

[SirLR]

I checked the gas cap and seemed tight and cleared codes already. I will end up checking the gas cap oring again and possibly replacing it. I found in the service manual how to diagnose so ill start with hoses and run the tests through techstream as well. I do not think its a fouled CC since I have no gas smell and engine runs great. I will diagnose and report back. The previous owner never changed the pcv so might as well do that aswell.

Just ran some diag today and I found out my vsv is perfect ran the active test through techstream and it pulls vacuum.

The hoses look fine from the engine bay side but the pcv definetly needs replaced will replace the hose with it aswell.

Now its onto smoke testing or pressure testing and possibly replacing the gas cap since I can't prove if its good or not, I'm gonna throw in a gas cap and pcv and hose and will report back with my findings after that Ill search for a shop to smoke test the lines and worst case replace the dreaded charcoal canister.

 

[SirLR]

Final Update: I threw in a brand new OEM gas cap and ran the EVAP test again in Techstream after clearing codes, and it didn't throw a pending, so successful fix. Thanks for all the help provided here.

 

[MyLC100]

I chased the same evap codes for several weeks. The codes threw traction warning lights on dash as well.

I bought a new gas cap as a quick easy fix but the codes continued. I replace all engine bay evap system valves, hoses and clamps (bought a hoses and clips on Amazon and valves from other auto parts sites). Several codes dropped after this effort but several persisted.

I finally narrowed down the issue to a failed switching valve at the charcoal canister. Toyota states this valve is part of the charcoal canister assembly and not available for sale individually. I did some digging into some other forums and found that Aisin VST-024 is a direct replacement option. I installed this Aisin switching valve, replaced the remaining rubber lines on the canister (above the spare tire) and all evap codes disappeared and have not returned in six months since replacing these components.

Probably $250 invested in all parts and too much of my time and sanity to get to the final fix.