Exhaust Gas Oxygen Sensor: Working, Replacement and Maintenance Tips

Exhaust Gas Oxygen Sensor: Working and Maintenance Tips

What is an Exhaust Gas Oxygen Sensor?

An Exhaust Gas Oxygen (EGO) sensor, also known as an oxygen sensor or lambda sensor, is an important component of a modern fuel-injected engine’s emission control system. It helps ensure that the engine operates efficiently and complies with emission regulations.

The engine control unit (ECU) receives input from the sensor as exhaust gases exit the engine and adjust the air-fuel ratio for optimal combustion. The sensor monitors the amount of oxygen in the exhaust gases as they leave the engine.

The EGO sensor is found mainly in the exhaust system, usually close to the catalytic converter or exhaust manifold. Most cars include at least two EGO sensors, one before and one after the catalytic converter. The exhaust pipe-inserted probe and wiring harness that connects to the ECU make up the sensor itself.

The EGO sensor creates a voltage signal based on the amount of oxygen in the exhaust fumes. The ECU uses this signal to modify the air/fuel ratio, which affects the engine’s emissions, fuel efficiency, and performance. The EGO sensor ensures that the engine operates effectively and that the car complies with emissions regulations.

How does it work?

The O2 sensor produces a voltage signal proportionate to the amount of oxygen in the exhaust gases. A platinum-coated ceramic element that serves as a catalyst is a sensor component. The platinum undergoes a chemical reaction when the exhaust gas contacts it, creating a voltage detected by the sensor’s electronics.


The engine control unit (ECU) uses the O2 sensor to modify the engine’s air/fuel ratio. The ECU can tell whether the engine is operating too richly or too leanly by measuring the amount of oxygen in the exhaust and then adjusting the fuel injection accordingly. This enhances engine performance while decreasing emissions and improving fuel efficiency.

O2 sensors come in two varieties: narrowband and wideband. Older vehicles employ narrowband sensors, which offer a constrained range of voltage signals that show whether the air/fuel ratio is rich or low. Wideband sensors are utilized in modern vehicles and enable a more accurate assessment of the oxygen concentration in the exhaust, allowing for more exact management of the air/fuel ratio.

When should you replace an Exhaust Gas Oxygen Sensor?

An EGO (exhaust gas oxygen) sensor is an important component of a vehicle’s engine management system. The following are some usual signs that could mean it’s time to replace an EGO sensor:

1. Check Engine Light:

Check if the engine light on the dashboard is turned on. This is the most typical sign that the EGO sensor is malfunctioning. The check engine light will turn on if the EGO sensor is broken or gives inaccurate information.

2. Low fuel efficiency:

A malfunctioning EGO sensor might make the engine run too rich (too much fuel) or too lean (not enough fuel), lowering fuel efficiency.

3. Rough idling:

A malfunctioning EGO sensor can make the engine stall or idle rough. This is so that the engine can function properly. The sensor controls the air/fuel mixture in the engine, so if it is not giving accurate information, the engine may not receive the proper quantity of fuel, air, or both.

3. Failed Emissions Test:

The EGO sensor is essential to ensure a vehicle’s emissions are within the permissible range. A malfunctioning sensor may result in the car producing more pollutants than it should, failing the emissions test.

Before changing the EGO sensor, having a qualified mechanic diagnose the issue is a good idea. EGO sensors should typically be replaced every 100,000 to 150,000 miles or as the car’s manufacturer instructs.

How to maintain the Exhaust Gas Oxygen Sensor?

The EGO sensor must be properly maintained to ensure accurate readings and ideal engine performance. The following advice will help you maintain an EGO sensor:

1. Keep it clean:

The EGO sensor’s function might be impacted by dirt and debris accumulation. The sensor can be carefully cleaned using a wire brush or a soft cloth.

2. Examine the wire:

Corrosion or damage to the wiring that connects the EGO sensor to the ECU may result in bad performance. Replace any wires that are corroded or damaged after routinely inspecting the wiring.

3. Replace it when needed:

Replace it when necessary because EGO sensors have a finite shelf life and may lose accuracy over time. The EGO sensor should be replaced every 100,000 miles or as soon as it malfunctions.

4. Observe the manufacturer’s instructions

When it comes to EGO sensor maintenance and replacement, abide by the manufacturer’s guidelines.

5. Use high-quality fuel:

Employ high-quality fuel because poor fuel might cause the EGO sensor’s performance to be negatively impacted by increasing carbon accumulation. To maintain a clean and accurate sensor, use high-quality fuel.

6. Check for exhaust leaks:

Inspect for exhaust leaks because they can lead to inaccurate EGO sensor readings. Examine your exhaust system for leaks and fix them if necessary.

By keeping your EGO sensor in good condition and using these suggestions, you can guarantee accurate readings and top engine performance.