Code P1135 O2 vs. A/F sensor?????

[amiru]

I have a 2001 RAV4 with less than 30K mi on it. Since the car was 2 months old, it started to do weird things, like wouldn't start and the dealer claimed they couldn't find the cause for over 3 days. Then, it had codes 420, 430 with the MIL on. The dealer reset it. Now, literally weeks after the warranty expired, MIL comes on again, and dealer says it's yet another problem, code P1135. The dealer wants over $600 to fix the A/F sensor that he claims went out. I am bloody suspcious that I've been having all this MIL crap going on, thinking, there's a bigger underlying problem. Some of my mechanic friends further confused me, because they claim there are no separate O2 and A/F sensors, it's really just one. Since the O2 sensor would have been covered under warranty, it really makes a big difference to know what is going on. Does anyone know what really causes P1135 to register in a very low mileage car, and does anyone know the relationship between the O2 and A/F sensors in a 2001 RAV4? I forgot to mention, although I'm not sure if it's relevant: our gas mileage seems to be WAY down since the dealer "reset" the sensor after the 420/430 codes four months ago.

[chronoti]

ummmm find some new mechanics that are part of the fuel injected age.

P0135 O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)

this code means that there is a heater coil in the O2 sensor that warms up the sensor when the engine is cold. these things operation temp are around 600 degreese f. if you have a ohm meter you can test the contacts on the sensor when it is cold for contiunity through 2 of the wires since it's cold the sensor wire wount give any feed back. this should also help with your gas milage. your air flow sensor is also called a MAP sensor and that is by your intake. the bad O2 sensor is the one right off the engine block in the exhust header.

[amiru]

Thanks, Chronoti, for you response! Are you absolutely sure that the P1135 code is NOT the A/F sensor, because the dealer showed me the DTC printout, and on it, it does say "+P1135 A/F Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)." So many "weekend mechanics" have mentioned that I should only replace the O2 sensor as a last resort, and of course, I have no idea what the relationship is between the O2 sensor and the A/F sensor. Other than the A/F sensor is not covered under warranty, and the dealer insists that the culprit is the A/F sensor, not the O2 sensor. Boy, would I love to get some sort of a proof to pinpoint the problem on the O2 sensor to ... well, shove it down their throats! Thanks again!

[chronoti]

the air to fuel sensor is the O2 sensor in the car. basicly it uses this to check the exhust to see how it's burning and controlls the A/F from that. sorry for some reason i was thinking air flow when you wrote A/F. but yes if you take it to some where else like auto zone or some other shops they will call it the O2 sensor. you can also try calling up the toyota dealer and ask them if the O2 sensor is the same as the A/F they more or less will say yes.

there are 2 o2 sensors in the car one right off the head and one if you look after the cat on the exahust. the one thats reading back bad is the front o2 sensor.

i'm not fully sure on the engine but you can search the site for this problem it might have been covered in the camry section since this also shares the camry engine.

[91 turbo]

The difference between an o2 sensor and an A/F sensor is that they work on different voltages. A/F sensors replace o2 sensors on newer vehicles. It is possible that your car has an A/F sensor which are alot more expensive.

[OEMonkey]

91 turbo is correct.
Also, look at your underhood ECS label and see if it's federal and cali certified. If you see california in there anywhere, then your Toyota uses an A/F sensor. The dealership makes that determination based on your VIN #. And there are quicker and faster ways to check the heater circuit. Resistance checks on some components are inaccurate. It sometimes checks out ok on the bench but fails under load. Technicians at the dealership know this as well and have prolly checked it after pulling the Pcode and FFdata and checking both LT and ST fuel trim as well as readiness monitors and any pending DTC's before concluding that you do need a new A/F sensor. Did your weekend mechanic friends do that for you and said that your sensor is ok and don't need to be replaced?
I don't know what kinda coverage you have on your warranty. But review it and see if it excludes coverage on the A/F sensor(but not the HO2S), or ask for a copy of your powertrain coverage detailing it. But it sounds like you have a lemon, if it's been giving you problems from the beginning.