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I forgot to mention, I also just noticed a vacuum hose was disconnected, the 1 that goes into the Air Filter Cover. I reconnected it. Reset the code by unplug battery. This car now has 150,000 miles on it. Radiator is new from toyota as of 2009.

Alright, I borrowed a scanner from autozone, and cleared all the codes, drove it for 2 days and the o2 codes have not come back, THE only code now is P0125, something about coolant flow or something. I have seen the check engine light turn off once while driving, then came back on and stays on. Same code P0125. I popped the hood and saw a FLAT upper radiator hose! I let it cool, took off the cap (which is new) and checked the fluid GREEn and smells fine, it was flushed 2 months ago. Any ideas why it is going flat, just an old hose, or is something else wrong? It just seems like 1 code now i can figure this out at home, really want to avoid taking it somewhere.

Thanks.

I just checked the wire harness connected to the Generic o2 sensor itself, i can't reach the one back to the ECM. I've been going to autozone and getting it checked by them. i think as long as i have older used vehicles im going to go buy a scanner right now :)

Did you ohm the wires back to the ECM? For continuity as well as shorts? I would look very closely at this. Once the wiring and O2 sensor has been eliminated, it would tend to point to the ECM being bad. So of course you will want to make sure before replaceing the ECM. Did you use a generic O2 sensor, or did you use a direct replacement? Of course closely checking all the hoses for splits or cracks is always a good idea. Y

Pulling the fuses, or disconnecting the battery works equally as well, (if you do not have a scanner). But the light will go out as soon as the problem is corrected (code will remain in memory for a short while). Do you have access to a advanced scanner, as opposed to a more basic code reader?

Thanks for confirming the location. I checked the wire and it looks good i have continuity on them all. Is there a proper or good way to reset this light? I dont want to have the stereo lock up or anything. But the last couple of times i just unplugged the battery for a short time. Does it need a HARD reset?

It sounds like you replaced the correct O2 sensor. And no, do not start looking at the Catalytic converter. Have you read the description of the code? Bascially the code is indicating that the output of the O2 sensor is not going high ocassionally. Since you have allready replaced the 02 sensor you should start looking at the wiring to the sensor. It is very possible that there is a bad connector, or one of the wires have been damaged. Since it is bank 1 sensor, it is very possible that the wire was damage on previous engine work (such as replacing the rear valve cover gasket). It is highly unlikely that the catalytic converter is causing the code.

As far as gas mileage, the O2 sensor problems are probably causing this. The computer tries to enrich the mixture in a effort to drive the O2 sensor high. If you have a advanced scanner, you would most likely find that both the short term and long term fuel trims are high. This means that extra fuel is being added in a attempt to drive the signal high. Find the O2 sensor problem, and the trims should return to normal.

Hi. This is my first post I've had the car for about 6months and it has been great, but the check engine light keeps coming on and off.

Ok so after i bought my 97 es300 a week later it started smoking blue ... iv never had a car do that so i was worried, but i HAD to drive it to my job about a 300mile trip before i got online and figured to check the PCV valve, of course that stopped the smoking immediately. I reset the computer by removing the + terminal on the battery and drove it, light came on again with codes... (P1030 and 0133 .. the usual ones) i bought a new O2 sensor and replaced it on the Firewall side (bank1 sensor 1 right?) so after that it still ran fine i guess light came on, got it scanned again and it kept having "transmission speed sensor code come up".. i replaced the speed sensor today 108.00. :( about 20 minutes of driving later the check engine light came back on .. speed sensor code is gone, now it has (P0125, P0130, P0133) Where should i go from here? I am thinking is the catalytic converter done? or should it be the other O2 sensors.

It all seems to be pointing to bank1 sensor1 not even 100% sure where that one is located.

Any help or experiences yall have had with this would be good.

Thanks.

P.S./ the major thing i have noticed it drives great starts right up... but gas mileage went from 420.0 miles per tank to 320.0