Hey whats going on guys,
Long time CL.com member here, just recently came across this forum and realized we have some knowledgeable people here
Here is my problem. I have 1997 ES300 with 102k miles. Had a check engine light go off, code P0135 (oxygen sensor 1 bank 1), I replaced the sensor closes to the firewall before the car. Was good for about 200 miles and light came back on again. Now I have code p0135 and p0420. I know 0420 is catlayst below threshold. But why p0135 again? Is it on because p0420 is on? I know p0420 is triggered via the rear o2 sensor (post cat). Should I replace this along with the cat? I just don't wanna spend money replacing stuff that is fine in order to track down this problem. I may just install an o2 simulator on the post cat sensor to avoid heavy repair costs. Any ideas or suggestions?