new_berlin

This is a 1998 ES300 whose check-engine-light came on suddenly while driving. Car functioned rest of the day (drove about 20 miles after the CEL came on) until the car got home.

I bought a OBD scanner and it shows the following code/s: P0440 01/02 (also there is an additional P0440 02/02 pending). The book that came with the scanner lists the P0440 issue as: H02S Heater COntrol Element High Bank 1 Sensor 3.

Based on the above, I figured that the internet would confirm that it's one of the O2 sensors but I am seeing articles/posts saying that P0440 is an Evap Related issue.

Is the scanner documentation wrong or should I accept the diagnosis? Also, does this particular code pose any safety concerns (i.e. is it safe and reliable to operate the vehicle while researching the issue)?

Thanks for any help. TIA.

EDIT: I made a mistake and referred to the wrong code. P0440 is indeed a EVAP issue in the manual. SORRY to create this thread.

DRACO A5OG

Hmmm,

Is that reader a Toyota aware reader or just a generic one?

In anycase, P0440 is supposed to be EVAP system related but it is strange the read out shows O2 Sensor Heater fault at the Sensor under the front seat at the exhaust pipe.

If Evap, you can drive it but you may suffer some fuel economy. If burnt out O2S then your care may run too rich or too lean. Too lean, can damage your engine, too rich and it could clog up the cats.

Check engine for loose or hard and brittle/cracked hoses, The canister described is the thing under the battery with two hoses. If you loosen one you should hear a swoosh of air. The other one will be silent. Then I would check each Vacuum solenoid for proper operation when 9 volt battery is put to in air blown thru. Save that for last, as it will require you to locate remove and test.

As far as the O2S, well, you can check the connector for looseness and to check for resistance but this will re quire you to remove it to get a better reading.

new_berlin

The model is Autel AL301, cheap so perhaps it's not Toyota aware. I did not realize that the same code can mean different issues depending on the car/manufacturer.

I will check the car per your suggestions tomorrow am. Thank you for responding.

DRACO A5OG

Keep us posted.

new_berlin

Sorry to report that I was wrong and was reading the wrong line in the manual. The manual does show P0440 as EVAP.

I looked at the hoses (they are small dia) connected to the cyclinder located under the battery. Visually they look ok but didn't come off easily. I will try again in a bit.

Btw, first thing I did was to check the gas cap, which wasn't obviously loose but I turned it a couple clicks. In the event that was the problem, will the CEL go off by itself soon or should I reset it and wait? Not sure which approach is recommended.

Again thank you all, and I apologize for reading the manual wrong (it's tiny writing.)

DRACO A5OG

Hey, we all done it from time to time. I was like hey hey, this is a new one

Well, I would replace the gas cap gasket or flip it around at a minimum and use some di-electric grease to help seal it better, just a little. If the rubber seal gasket on the gas cap is hard and brittle, definitely change the rubber or buy an aftermarket one, they are fairly cheap.

Yes, it will turn off by itself after 100 miles or so after it no longer reproduces that fault. If you want to know for sure, disconnect negative side and after 200 miles, if not CEL, you fixed it :-)

Good idea to clean the cap and neck every time you fill her up. I bet it is dirty as sin :-)