Technician A says that closed loop is the most efficient operating mode and allows the engine computer to control the air-fuel ratio with the most precision. Technician B says that open loop operation is used to improve performance during cold engine warm-up and is also used under heavy load or during wide open throttle operation. Who is correct?
A) Technician A only
B) Technician B only
C) Both technicians
D) Neither technician

Question

Quizplus · Accepted Answer

Both technicians are correct. Technician A is correct in stating that closed loop operation allows for the most efficient and precise control of the air-fuel ratio by the engine's computer. Technician B is correct in stating that open loop operation is used during conditions where the engine needs to warm up or is under heavy load, such as during wide open throttle, where the engine might not rely on the oxygen sensor feedback for fuel control.

Technician a Says That Closed Loop Is the Most Efficient