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lexpert
lexpert, Lexus Master tech
Category: Lexus
Satisfied Customers: 2100
Experience:  Master Certified with lexus, 8 years experience with Lexus
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RX400H keeps throwing codes P0441 and P1421. Already

Customer Question

RX400H keeps throwing codes P0441 and P1421. Already replaced gas cap new factory cap, and I replaced the Vacuum Control Valve by the intake with used one. Codes still intermittently come back.
JA: Has the vehicle turned into a gas hog? And how does it start -- same as usual?
Customer: I haven't notice a difference in gas mileage , but it does sometimes act lick the tank is not seeing the vacuum because it vents gas fume out the cap and some make you wait to open the the gas door over the cap.
JA: What is the model/year of your Lexus?
Customer: 2006 RX400h
JA: Are you fixing your vehicle yourself? What have you tried so far?
Customer: Yes I was tying to fix it myself, as I said, I changed the gas cap and Vacuum control valve. I also changed out some Vacuum lines by the Control valve.
JA: Anything else you want the mechanic to know before I connect you?
Customer: How much does this cost?
JA: I'm not sure of the exact price, but there's only a $5 deposit. The rest of the price information will be on the page I send you to.
Customer: ok,, let me see
Submitted: 7 months ago.
Category: Lexus
Expert:  david craig replied 7 months ago.

Hi Im David, please allow mw a few minutes to review your information on the vehicle. thank you

Expert:  david craig replied 7 months ago.

P0441 LEXUS - EVAP System Incorrect Purge Flow- replace the purge valve.

P1421 LEXUS - EVAP Canister Gross Leak-replace the purge valve.

Customer: replied 7 months ago.
Hello David,
If you are talking about the valve up on the intake, have already tried a different Purge Valve as I said in the correspondence with the JA
"RX400H keeps throwing codes P0441 and P1421. Already replaced gas cap new factory cap, and I replaced the Vacuum Control Valve by the intake with used one. Codes still intermittently come back.
JA: Has the vehicle turned into a gas hog? And how does it start -- same as usual?
Customer: I haven'tnotice a difference in gas mileage , but it does sometimes act lick the tank is not seeing the vacuum because it vents gas fume out the cap and some make you wait to open the the gas door over the cap.
JA: What is the model/year of your Lexus?I think this is important from the message above "I haven'tnotice a difference in gas mileage , but it does sometimes act lick the tank is not seeing the vacuum because it vents gas fume out the cap and some make you wait to open the the gas door over the cap."
Expert:  david craig replied 7 months ago.

the vacuum control valve is not the purge valve

Customer: replied 7 months ago.
where is this valve?
Expert:  david craig replied 7 months ago.

i will send you the diagram of where it is.

Expert:  david craig replied 7 months ago.

I hate lexus sometimes. the purge valve is called a vacuum switching valve on them . my apologies.

Customer: replied 7 months ago.
I sent a picture of the valve that I changed out
Expert:  david craig replied 7 months ago.

yep. thats it. did you check it electrically before replacing?

Customer: replied 7 months ago.
that appears to me from the diagram where the valve was that I changed. The middle of that bracket.
Expert:  david craig replied 7 months ago.

ok. are you sure the used one was working?

Customer: replied 7 months ago.
no I did not, but i do know that it is not stuck open.
Expert:  david craig replied 7 months ago.

well with out checking it electrically by applying 12vdc to it to verify that it does open we can only assume its working. the next step in troubleshooting the system is to have a smoke test performed to find any leaks within the evap system.

Customer: replied 7 months ago.
as I said, the tank to me appears to be not getting vacuum to it and it is over pressurizing at times. then it will vent out the cap like a relief valve.
Expert:  david craig replied 7 months ago.

the gross leak at the canister needs to be addressed before chasing p0441.

Expert:  david craig replied 7 months ago.

the last word of that paragraph is "canister.":

Expert:  david craig replied 7 months ago.

P1421 This diagnosis detects leaks in the Evaporative Emission System (EVAP) purge line using engine intake manifold vacuum. If pressure does not increase, the Engine Control Module (ECM) will check for leaks in the line between the fuel tank and EVAP canister purge volume control solenoid valve under the following vacuum test condition. The vacuum cut valve bypass valve is opened to clear the line between the fuel tank and the EVAP canister purge volume control solenoid valve. The EVAP canister vent control valve will then be closed to shut the EVAP purge line off. The EVAP canister purge volume control solenoid valve is opened to depressurize the EVAP purge line using intake manifold vacuum. After this depressurization is implemented, the EVAP canister purge volume control solenoid valve will be closed.

Customer: replied 7 months ago.
Is the Key-off Monitoring System something that is done automatically when the car sits?
Expert:  david craig replied 7 months ago.

after the car sits, it will be ready to be monitored with a scan tool.

Expert:  david craig replied 7 months ago.

i believe you need to check the charcoal canister for any visual evidence of damage. i.e. cracks, broken connections also.

Customer: replied 7 months ago.
key word scan tool, then I cant do this myself.
Customer: replied 7 months ago.
do you have a vacuum diagram showing the complete evap system?
Expert:  david craig replied 7 months ago.

i think i can get that for you. allow me a few moments

Expert:  david craig replied 7 months ago.

here a layout for you.

Expert:  david craig replied 7 months ago.

Do you still need assistance?