How to trick downstream o2 sensor
Shanna hoarders
Oct 30, 2020 · The front O2 sensor measures the mixture, and it tells the engine control unit if the engine is running with a rich or lean mixture and adjusts it. The rear O2 sensor is just a diagnostic O2 sensor for the p0420 code. If the rear O2 sensor is getting faulty values, the p0420 code will get stored in the engine control unit.
I tested the ECU wires (black and yellow) on the harness connector pins on both downstream O2 sensors. The working O2 sensor gave a reading of 0.060 v The not working sensor gave a reading of 0.000 v. I have noticed the car starts rough EVERY SECOND TIME.