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Ron Z.
Ron Z., - Lexus Tech -
Category: Lexus
Satisfied Customers: 18773
Experience:  18+yrs experience. State Inspector and Lexus Diagnostics
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Diag codes with passing emissions. : reset codes at

Customer Question

diag codes with passing emissions.
JA: Sometimes things that you think will be really complicated end up being easy to fix with Lexus. The Lexus Mechanic I'm going to connect you with knows all the tricks and shortcuts. Tell me a bit more about what's going on so he can help you best.
Customer: reset codes at autozone. need to know how far to drive car to complete a cycle
JA: Are you hoping to fix this yourself?
Customer: yes
JA: Great! What have you tried so far?
Customer: reseting codes at autozone
JA: Is there anything else important you think the Lexus Mechanic should know about your Lexus?
Customer: no
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Lexus Mechanic about your situation and then connect you two.
Submitted: 1 year ago.
Category: Lexus
Expert:  Ron Z. replied 1 year ago.

Did you have "p-codes" stored that caused you to fail the emissions test?

Customer: replied 1 year ago.
one sec
Expert:  Ron Z. replied 1 year ago.

Ok. If you have those codes, that'd help a ton.

Customer: replied 1 year ago.
p0031 and p0455 EVAP Control System Leak Detected (gross leak)
Expert:  Ron Z. replied 1 year ago.

Ok. Did you make any repairs to try and correct these?

Customer: replied 1 year ago.
Customer: replied 1 year ago.
just went to Emissons and failed. Went to Autozone to replace battery.
Customer: replied 1 year ago.
the codes I gave you were from the Emissions center paperwork
Customer: replied 1 year ago.
I just turned off car and switched to on , then removed the gas cap and replaced it. I listen to insure it clicked 3 times
Customer: replied 1 year ago.
the check engine light came back on after replacing the battery 20 minutes ago. my fear was that a cycle reset would occur after I had Autozone guy reset codes.
Customer: replied 1 year ago.
but they are back now
Expert:  Ron Z. replied 1 year ago.

Ok, great. So, let's start with your question- After clearing the codes (or replacing the battery) this resets the on-board computer and you then need to do a "Drive Cycle". This is roughly 50-75 miles of combined city and highway driving. HOWEVER, is the codes were not addressed or were not fixed properly, before you get the Drive Cycle finished, the Check Engine Light WILL return, and you'll be right back in this same spot. So you'll need to address the codes first... THEN do the drive cycle... THEN return for re-inspection.

The P0031 is a fairly common problem. It points to a problem with the Upstream Oxygen Sensor. Very common wear and tear fail item. If the wire harness and connector look good, replacement is usually the answer.

The P0455 is a large EVAP Leak. Very commonly this is a faulty Fuel Cap. Make sure it is tight and seated correctly. Check the underside of the fuel cap for any cracks or signs of defects that may keep the cap from sealing correctly. If there are any doubts about the inspection of the cap, replace it. Keep in mind, you will need a cap that meets OE Specs. Those "universal" or "locking" fuel caps sold at after market parts stores do not meet OE specs, and will not seal the system correctly. If you are sure the cap is good, then an EVAP System "smoke" test will be needed. This is where a machine forces smoke through the system and any leaks can then be easily found and repaired.

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Expert:  Ron Z. replied 1 year ago.