Code PO171, fuel consumption high?

I looked at my old one and it says Toyota and Denso.

So, I did the 3x 4,000 RPMs test and the sensor one voltage never got to. 45v. The highest was about.2v. Did it live data because there doesn't appear to be a freeze option? Also watched fuel trim go from 19% down to about 3-4% when revved and hit zero but not go negative and then return to 19%. I don't really know what any of this means and I'm starting to feel defeated on this one. I would like to try both sensors from a parts car. Point of interest, I was working on a Jeep Patriot so I decided to watch live data. Fuel trim numbers were going from 3% to negative %s on sensor #1. Sensor #2 was same as mine at 99%. I also read that it's sensor #1 that's responsible for fuel trims because it's reading oxygen levels pre- catalytic converter. Could this issue be with sensor #1? The only reason I suspected #2 was because there was no output voltage.

Isn't this fun, lol.

I'll keep you posted. That's why I like the simplicity of my 64 Dart.

Here we go. I have no ground to the heater of sensor 2. If I create a ground the heater works but still running open loop. Is there an O2 sensor fuse in this car?

The ground for sensor 2 is pink. Where does this wire originate? It seems to come from a main group of wires under the dashboard. Is it supposed to come from the ECM? If I can talk the boneyard into letting me try an ECM from another Corolla of the same year, do I have to reflash it? Also, the heater is turned off by the ECM when the exhaust gas reaches 600F so would/could no ground cause this issue? Is it more likely a failed ECM? Kind of lost here?

Thanks. I'm really not one to just throw parts at a problem. If I run a direct ground to the heater circuit, I still get open loop fuel system 1. What do you make of this?

I can get a used ECU for $20, but I'm trying some other things first. Denso sensor and thermostat. Is it the temperature sensor on the t-stat housing or the one under the 1, 4 coil that sends information to the ECU?

I was just reading that large leaks in the evap system can drastically affect fuel efficiency. My evap lines are basically rotted away in back by the tank and have holes under the driver's area. Could this cause any other codes to be set off other than po455 which I don't have. The only code I keep getting is po125. Thanks

That's the one I replaced but now I put the original one back in. Wish this car had a Schrader valve on the fuel rail instead of needing a special adapter to test fuel pressure and see if I might have a leaking injector.

I have some new info. I do have a ground to the heater from the ECM when the engine is running. I put the old O2 sensor back in and once again have no voltage output. I also put my ECT back in and compared it to the new one and they were basically the same. I checked ohms readings in the wires from the ECT. I got the following values on a basically hot engine. Between the yellow/green wire and the white wire there was 550ohms, between the brown and white 500ohms, and between the yellow/green and brown 50ohms. The coolant temperature was 97 degrees C so plenty hot to run closed loop. The code is PO125. I don't think the ECT info is going to the ECM. I'm going to check ohms readings in those wires at the ECM if I can find them. Do they run the same colors to the ECM? Please let me know what you make of this new info. Thank you.

225 Slant 6. Push button Trans, ragtop 270 model. Not perfect but runs good and simple.