Lexus Troubleshooting Questions? Ask a Lexus Expert
Do you have the specific code numbers and has there ever been any other code in the engine control computer besides the oxygen sensor code?
The P1120 and P1121 should have anything to do with the oxygen sensor. That strictly a code setting because of a malfunction in the accelerator pedal position sensor circuit. It could be an intermittent problem. That's what causes it to go into limp mode when it doesn't see the proper input from that sensor on the throttle body. Did you replace the oxygen sensor for bank one sensor one with a new DENSO brand sensor and does your code reader allow you to read live data as you can monitor the voltage output of the sensor? At the engine side of the harness to B1S1 What is the voltage at the Black wire with the red tracer with the key on? Then check the green wire with the key on. What is that voltage on the light green wire with the car running?
The color coding of the wires going to the sensor that you just explained being the green with black tracer is for bank one sensor two. That would set a P0141 code you need to find bank one sensor one and the wire color coding should be as I described. Then check the voltages as I described on the R/B wire and the light green wire.
Just checking back with you to see if you got the last reply that I gave you that the sensor you were checking was the wrong one. Were you able to test the voltage on the correct sensor on the color-coded wiring that I gave you?