When does the ECM set the P0420 code?
When does the ECM set the P0420 code? When the ECM/PCM sees the downstream O2 sensor switching at or near the same rate as the upstream O2 sensor, it sets the P0420 code. What Does the P0420 Code Mean? Where is the P0420 OBD2 trouble code stored? 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 this trouble code. If the rear O2 sensor is getting faulty values, the p0420...