Toyota AF oxygen sensor ohms

Thanks Chad for your reply. Let me give a little background of the car maybe it might help you understand the problem better.
When I bought the car there were no CAT DTC’s, the inspection paper showed DTC’s for 3 sensors and camshaft position sensor DTC. The camshaft position sensor was fixed by cleaning off the debris and the code never came back.
The previous owner workshop gave quotation for CAT and ECU, Toyota dealership gave same quotation without both workshops carrying out any diagnoses on the ECU other than following the service bulletin procedure.
There were no CAT DTC at the first workshop, they only call for a change of ECU and CAT as a result of high CO/HC base on the quotation paper the owner gave me. They were CAT DTC’s when Toyota checked and gave ECU and CAT quotations.
The DTCs at the time of buying the car were P1155, P1135, P0161. I checked the resistance on all the 3 sensors and got nothing, so I decided to change all the 4 sensors, at this point no CAT DTC’s, but one thing I noticed which I’m not sure why they did that was that all 4 sensors that came with the car when I bought it were cut and taped with black tape. Fast forward to like 1yr later I decided to just play around with the taped sensors and I removed all the tapes and then measure the sensors again and they all gave accurate resistance readings this time. I have tried to find out from the previous owner why the sensors were taped, and what sort of job was done at that end, but the lady couldn’t give any answer.

As soon as I installed all the 4 new OEM sensors, then the CAT DTC’s appeared, so I thought maybe the CAT had been destroyed as a result of the previous owner driving with 3 non-functioning sensors. I bought a used CAT and the driveability problem still remained and within a week the CAT DTC’s appeared again on the second hand CAT.

As for the ECU I have done the voltage checks outlined in the repair manual and the ECU is giving out all accurate voltages. Is it possible to have a bad ECU that is giving out the proper voltage or is the ECU suffering from calibration problem.

The drive symptoms of my car is a direct replica of a friend’s car I went to buy with him. I noticed the poor movement of the car and whilst on our way home the check engine light popped up because the seller probably erased it just to sell the car. It was an oxygen sensor DTC and after it was changed the car drove fine. In my case the confusion on my upstream sensors is coming from
1. The previous sensors read 1.1ohms, but I’m not sure if those were the sensors that came with the car from the factory or they just went to buy some sensors from junk yard that are not the specifications for this car since the sensors were taped.
2. I’ve checked another 2002 model of this car and the upstream sensors read 1.1ohms
3. The repair manual I bought online lumped together 2001-2007 models which doesn’t help to know exactly the part (ohms) for my specific 2002 model.

Finally it’s quite unfortunate that no mechanic in Sweden knows what an exhaust back pressure is, I’ve asked more than 5 mechanics and they don’t even have the gauge.

I don’t know if you can make something out of this.

hi sir really quikly without any research is it possible downstream sensors are traditional zirconium narrow band sensors