Oxygen Sensors

To keep the engine running efficiently, extracting as much power from a given charge of fuel and oxygen, the engine control module (ECM) monitors the oxygen content of the exhaust, using oxygen sensors to determine how much to adjust fuel injection. Oxygen sensors react to the oxygen content in the exhaust, comparing it to that in the air. Since the implementation of automotive on-board diagnostics systems, various forms of OBD since 1968, and federally-mandated OBD2 since 1996, oxygen sensors have been at the forefront of monitoring engine performance and efficiency.

The modern OBD2 ECM uses multiple oxygen sensors, sometimes referred to as air-fuel ratio sensors, to fine-tune engine performance and efficiency. Additionally, oxygen sensors after the catalytic converter are used to monitor the catalytic converter function.

• When there is high exhaust oxygen, this means that too little fuel is being injected, which is referred to as a lean mixture. To improve engine performance and prevent unburned fuel from getting into the atmosphere, the ECM increases fuel injection.

• When there is low exhaust oxygen, this means that too much fuel is being injected, which is referred to as a rich mixture. To prevent engine damage and the production of nitrogen-oxide pollutants, the ECM decreases fuel injection.

The ECM constantly compares oxygen sensor readings before and after the catalytic converter. In general, while the forward oxygen sensor readings are constantly fluctuating, switching from rich to lean to rich every second or so, the rearward oxygen sensors shouldn’t fluctuate much at all.

• If the oxygen sensors before and after the catalytic converter read the same, this indicates that the catalytic converter isn’t functioning properly.

How Can In ’N Out Car Services Help?

• Determine if your oxygen sensors are causing your problem

• Utilize diagnostic tools in testing sensors

• Replace your oxygen sensors