Open Loop vs. Closed Loop

[Griz64]

Hey guys. I recently got a Scangauge 2 which I love. One of the functions of the Scangauge is to be able to tell you when you are in open or closed loop. My basic understanding of closed loop means that the trucks computer is using the O2 sensors to regulate the fuel flow to the injectors and open loop just puts the gas in the the throttle body like an old carb. I know there are other functions as well but that is a very basic idea of Open vs Closed loop. Am I right or wrong in my understanding? After hooking up my scangauge I noticed that everytime I touch the gas pedal it goes right into Open Loop and as soon as I let up it goes to closed loop. In short my truck goes into open loop when accelerating and closed loop when decelerating. Assuming my understanding of open and closed loop, is it right to go back and forth between open and closed like it is or is this something that needs to be looked into??? Thanks for any and all light shed on this subject.

[Q-Hack!]

What does it do at steady throttle on the highway?

[H2OPWR]

Hey guys. I recently got a Scangauge 2 which I love. One of the functions of the Scangauge is to be able to tell you when you are in open or closed loop. My basic understanding of closed loop means that the trucks computer is using the O2 sensors to regulate the fuel flow to the injectors and open loop just puts the gas in the the throttle body like an old carb. I know there are other functions as well but that is a very basic idea of Open vs Closed loop. Am I right or wrong in my understanding? After hooking up my scangauge I noticed that everytime I touch the gas pedal it goes right into Open Loop and as soon as I let up it goes to closed loop. In short my truck goes into open loop when accelerating and closed loop when decelerating. Assuming my understanding of open and closed loop, is it right to go back and forth between open and closed like it is or is this something that needs to be looked into??? Thanks for any and all light shed on this subject.


Actually Open loop is when the ECU is injecting fuel according to a pre determined fuel table. The input from the O2's is ignored for one reason or another. The Ecu will be in open loop when the vehicle is first warming up allowing the O2's to get up to operating temperature. The ECU will also trigger open loop when you are slowing down and then it shuts off your fuel injectors to conserve fuel. Those are the only two times open loop is desirable. The pre programed table is set to max rich so you will not run into a lean burn condition and over heat your motor. This reduces fuel economy by quite a bit and means that there is a faulty sensor somewhere. It usually will trigger a check engine light.

Larry