How does the O2 sensor work in an OBD-II?
How does the O2 sensor work in an OBD-II? This code is triggered by the first downstream (front) O2 sensor. The sensor provides a reading of the air:fuel ratio leaving the engine's cylinders, and the vehicles powertrain/engine control module (PCM/ECM) uses that reading and adjusts to keep the engine running at that optimum ratio of 14.7:1. What causes a lean reading on an O2 sensor? High (O2) content in exhaust equals a lean reading also causing engine misfires. There are also some other possibilities such as an internally leaking EGR system. This will typically set a separate code. A leak...