CEL P0171, sensor questions.

[sethster]

Hello. I have a 2003 Toyota Solara, equipped with the 2.4 liter 2az-fe engine, and it is in California so I imagine it is a CA model. I have been getting a CEL for over a year now. It is code P0171 too lean (Bank 1, Sensor 1). I have noticed that the car does have some spark knock at low speeds and uphill every once in awhile too.

I am trying to figure which sensor is (bank 1, sensor 1), and whether it is an air/fuel ratio sensor, or an oxygen sensor. I have called Autozone, the local Toyota dealer, small Autoparts stores, and they all give me different answers. Here are some pics:

Which sensor is this?


And which sensor is this?


And, is there another sensor after the catalytic converter? If so, which is it?

So far I have replaced the spark plugs, tested for vacuum leaks, cleaned the MAF sensor, cleaned the Fuel Injectors, Cleaned the Throttle Body, and still the CEL comes back on after about 250 miles of driving after resetting it.

Does anyone have an answer to my questions or some guidance here?

[Akfahad]

use the search function, I'm pretty sure this has been talked about...but if I'm not mistaken, your first picture is an A/F sensor, the second pic is an O2 sensor.

[sethster]

Thanks but I have searched extensively on here and I could not find what I was looking for. Every thread I bring up is for a different generation or engine. Im just looking for some set in stone information because like I said everytime I call the dealer or Autozone I get a different answer.

The guy at Toyota actually told me that HE WAS 100% positive that my car did not have a sensor after the catalytic converter. Now, everyone I seem to talk to says that thats impossible in California. Autozone said I have one there too. Thats why im asking here.

But, if nobody knows here either then I guess I am just SOL and will have to look elsewhere. The mystery continues

[sethster]

Well I failed to realize that this car has two catalytic converters. The one in the first pic is Sensor #2, and the one in the last pic is sensor #1.

I replaced the b1s1 today, I will update if the code comes back again.

[sethster]

Just an update. I have driven approximately 1000 miles so far and no CEL anymore. I replaced the B1S1 with a Bosch brand one (not OEM). This must have fixed my problem.

The only other thing I did at the same time was clean and re-oil my K&N Drop in Air Filter, and then I cleaned the MAF after driving 100 miles or so in case any of the oil got on the sensor.

[steffknee]

You probably have a bad MAF sensor.

P0171 isn't necessarily an O2 sensor. And I would have to say usually when your O2 sensor is bad, it's just bad and the light won't go on and off over such a long period of time.

Try cleaning out the MAF sensor and See what happens.

Oh, and I believe the first (second picture, top sensor in the cat) is an O2 sensor and the second (first picture, sensor after the cat) is an A/F sensor.