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Ron Z.
Ron Z., - Toyota Tech -
Category: Toyota
Satisfied Customers: 17972
Experience:  18+yrs experience. State Inspector and Toyota Diagnostics
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HIghlander: I have a 2003 Highlander, V6 all wheel drive.

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I have a 2003 Highlander, V6 all wheel drive. My check engine light came on and I went to Autozone, they ran their diagnostic and I got three codes; P1135, P0446 and P0440 - they told me it was an O2 sensor that needs to be replaced -Bank 1 Sensor 1 - does that sound right?
Hello! Welcome to the site! Thanks for coming! I'm Ron Z. I'm here to provide as much info and insight as I can, to best answer your question.

Can you re-check the P0440 code. This is not a valid code for this year/model vehicle. Perhaps it was P0441?






Customer: replied 3 years ago.

The print out that Autozone gave me says P0440, P0446 and P1135

OK. AutoZone uses a "generic" scan-tool, so the P0440 is more than likely just a by-product of the P0446 (the P0440 is not a valid code on this vehicle, however, it IS on other vehicles, and is very similar to the P0446).

Ok... anyway...

Looks like you have 2 different problems here.

The P1135 is a very straight forward code pointing to a faulty A/F Sensor (very similar to an Oxygen Sensor, just "smarter" as Toyota uses it's inputs for more functions). This is a very common Toyota fail item. The sensor is located on the side of the engine closest to the windshield, mounted to the exhaust manifold. Carefully inspect the electrical connector and as far up the harness as you can looking for any loose, broken or damaged wires (very rare, but always good to check!). If the visual inspection checks ok, replacing the A/F Sensor will solve the problem. Keep in mind- it must be an "A/F Sensor" and Oxygen Sensor will not do the job correctly!
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The P0446/P0440 is a bit more difficult to diagnose. P0446 is recorded by the ECM when there is an evaporative emissions leak from the components within the EVAP system, or when there is a malfunction in the VSV for EVAP, the VSV for pressure switching valve or in the vapor pressure sensor itself. Best place to start here is to have the EVAP System "smoked". This is where a machine forces smoke through the system, and any leaks will reveal themselves. If the smoke test shows no leaks, then unfortunately, each item listed above will need to be tested. More times than not, it's a faulty VSV, so these should be tested first.
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