OBDII Automotive Articles - Difference Between Open Loop and Close Loop

Difference Between Open Loop and Close Loop

- Edited: Apr 07, 2022
- Popularity: 5,457 Views

What Difference Between Open Loop and Close Loop Means:

When the engine is cold and is started or there is a malfunction with the engine, the engine operates in an "Open Loop" meaning that the Engine Control Module (ECM) will ignore most of the sensors reading and use predefined parameters set by the factory to control the engine, more specifically the engine’s air/fuel mixture. This "Open Loop" operation allows time for the engine to come up to a normal operating temperature before it starts using the information from the sensors to adjust for driving conditions. Once the engine is warm-up or reaches normal operating temperature and there are no engine malfunctions, the ECM will start controlling the engine in "Close Loop", meaning that the ECM will receive the signals from the Oxygen Sensor, Coolant Temperature Sensor, and other engine sensors to control the engine's air/fuel mixture.