Ls 430 2004 model with 130,000 miles mileage; Bank 1 STFT fuel trim is stuck at +19.5 during idle and does not move on either side even at higher RPM. O2 sensor bank 1 sensor 1 was recently changed however still P0134 is being popped up intermittently. Car is running fine though. Any help is greatly appreciated. Thanks😊

 

Check that side for a vacuum leak or fuel pressure errors, make sure the sensor you used is an OE or OE equivalent or it may not provide the right value to the ECU. The fact you still have a code means it may not be a correct sensor or you have other, more major issues involving the harness or ECU.

If the car is adjusting up that usually means too much air is entering or being metered low.

 

Can you read live data with your scanner? Make sure the O2 sensor is switching and reading it's full range. Could be an incorrect or contaminated sensor like striker said above. Your problem isn't likely a vacuum leak as the short term correction would be less at higher rpms. Another possibility is a dead or weak fuel injector on that bank. You can do an injector balance test to rule that out if you can find the required tool. There are videos online on how to do the test.

 

Thanks for the advice. The sensor I used is an OE one. However upon checking live data, O2 sensor reading is intermittent. O2 is completely dead sometimes. I checked 02 wiring and harness which seems ok. Can’t figure out what’s the real issue is.

 

Without getting too far into the internet guesting game, do you have an obd reader with data logging capabilities? Something like an obdlink mx dongle with and app like car scanner?

If so can you get say 10 minutes of driving with all
4 o2 sensors,
maf,
throttle position,
ltfts,
speed
engine temp
and rpm?

My gut feeling based on description is both O2's sensors 1's need replacing with new densos or lexus parts (as a pair), but it is hard to say for sure without real data to back that hunch up cause it could be a few other things too (looking at you maf).