Oxygen sensors in diesel engines are primarily used to adjust which parameter?

• A. Air-fuel ratio
• B. Engine torque
• C. EGR flow
• D. Turbo boost

Answer: (A)

Oxygen sensors provide feedback on the exhaust’s oxygen content, and the engine control unit uses that information to fine-tune how much fuel is injected. This closed-loop adjustment targets the air-fuel ratio, ensuring efficient combustion and proper aftertreatment operation. In diesel engines, while they run lean, the sensor still guides fuel delivery to achieve the desired lambda and emissions performance, rather than directly setting torque, EGR flow, or turbo boost. Those other parameters are managed by separate systems and sensors, whereas the oxygen sensor's primary role is to regulate the fuel amount to control the air-fuel ratio.