Please explain closed loop and open loop to me
Thread Starter
Joined: Nov 2001
Posts: 3,406
Likes: 2
From: Tallahassee, Fl
Please explain closed loop and open loop to me when do these occur and what do they do
im having a problem with my car for the first 3-4 minutes after starting it, whether the motor is warm or cold, and im trying to track it down
im having a problem with my car for the first 3-4 minutes after starting it, whether the motor is warm or cold, and im trying to track it down
Staging Lane
Joined: Aug 2002
Posts: 69
Likes: 0
From: California
Re: Please explain closed loop and open loop to me Closed Loop indicates that the PCM is controlling fuel delivery according to oxygen (O2) sensor voltage. In Open Loop, the PCM ignores the oxygen sensor voltage and bases the amount of fuel to be delivered on throttle position (TP) sensor, engine coolant, and MAF sensor inputs only.
TECH Enthusiast
Joined: Oct 2003
Posts: 729
Likes: 0
From: Bakersfield, Ca.
Re: Please explain closed loop and open loop to me Forgive my ignorance too on this. I am new to this too and learning that has a huge learning curve. 
Is there specific times when we should see open loop status?
@ idle load/no load?
@ WOT?
@ cruising down hill?
I am going through the tune list on ls1edit.slowcar.net and just made my first Ltrims adjustment this morning (110%), and I went way out of adjustment, so I backed it out and went half way 105% and things look much better. But since I was used to the stock programming, I am not sure when I should be seeing opening/closeing loop.
I am seeing closed loop all the time now at idle when it used to be open before.
Thanks in advance,
Paul.
Is there specific times when we should see open loop status?
@ idle load/no load?
@ WOT?
@ cruising down hill?
I am going through the tune list on ls1edit.slowcar.net and just made my first Ltrims adjustment this morning (110%), and I went way out of adjustment, so I backed it out and went half way 105% and things look much better. But since I was used to the stock programming, I am not sure when I should be seeing opening/closeing loop.
I am seeing closed loop all the time now at idle when it used to be open before.
Thanks in advance,
Paul.
TECH Senior Member
Joined: Nov 2001
Posts: 7,036
Likes: 1
From: Lake Zurich, IL
Re: Please explain closed loop and open loop to me I believe open loop is used at startup (until O2 sensors come to temp) and at WOT (PCM has a table it uses for fuel delivery, and it uses the LTRIMs to determine if fuel should be deleted or added across the board)
TECH Enthusiast
Joined: Oct 2003
Posts: 729
Likes: 0
From: Bakersfield, Ca.
Re: Please explain closed loop and open loop to me Thanks Mike.
I also found this
https://ls1tech.com/threads/showthre...mp;o=&vc=1
Which I am surprised I didn't find before.
I also found this
https://ls1tech.com/threads/showthre...mp;o=&vc=1
Which I am surprised I didn't find before.
TECH Resident
Joined: Jan 2002
Posts: 754
Likes: 0
From: USA
Re: Please explain closed loop and open loop to me Pre OBD-II ECMs functioned in only two modes, open or closed loop.
With OBD-II there is 7 modes,
open/closed and then 5 sub modes.
Open loop is below about 130 degrees and once conditions have been met then PCM switches to closed loop and stays there.
It does not go back to open loop for PE/WOT as OBD-I did, rather shifts into PE sub mode while still in closed loop.
This can be shown by scanning with the engine loop PID.
With OBD-II there is 7 modes,
open/closed and then 5 sub modes.
Open loop is below about 130 degrees and once conditions have been met then PCM switches to closed loop and stays there.
It does not go back to open loop for PE/WOT as OBD-I did, rather shifts into PE sub mode while still in closed loop.
This can be shown by scanning with the engine loop PID.
