OBDll Scanner Live Data
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Junior User
Joined: Mar 2007
Posts: 59
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From: Texas
OBDll Scanner Live Data
On OBDll Live data what do the ST FTRM1 %, LT FTRM1 %, ST FTRM2 %, LT FTRM2 % mean... what is that for what does it read what is it used for how can you use it trouble shoot any problem etc...basically any info on those readings did use scanner but didnt know what they were for. Am curious as to what its function is... & what would be some good readings on it, I got around -7.8 to pos 4.4 or so but sometimes it would just jump to 38pos. & so on....any info thanks!!!!!
Cargo Master
Joined: Apr 2003
Posts: 3,476
Likes: 224
From: Frequently frozen MN
I believe that those are the short and long term fuel trims for each bank of cylinders.
Short term means that it reacts to the current situation. Basically, the O2 sensor tells the computer how things are going, and the computer changes the fuel trim to get the mixture closer to ideal.
Long term is supposed to react to a long term trend in the short term reading. It's supposed to adjust for wear, etc. When long term adjusts, the short term numbers SHOULD drop.
As to the ranges, etc., you'll have to wait for somebody to respond that actually knows what they're taling about. Or, you could try to research it online.
Short term means that it reacts to the current situation. Basically, the O2 sensor tells the computer how things are going, and the computer changes the fuel trim to get the mixture closer to ideal.
Long term is supposed to react to a long term trend in the short term reading. It's supposed to adjust for wear, etc. When long term adjusts, the short term numbers SHOULD drop.
As to the ranges, etc., you'll have to wait for somebody to respond that actually knows what they're taling about. Or, you could try to research it online.
Hotshot
Joined: Jan 2004
Posts: 19,762
Likes: 1,079
From: St Louis
To do some research, go to www.motorcraftservice.com and click on the "OBDII Theory and Operation" tab on the left side.
The manual for your specific year's model will be a treasure trove of background information.
The manual for your specific year's model will be a treasure trove of background information.
Senior User
Joined: Nov 2004
Posts: 357
Likes: 0
From: Lancaster, PA
Rich mixture = lean correction and a negative value on your live data. Then a lean mixture will have a positive Rich correction value. Numbers should be within 20-25% based off of a 0 baseline (equivalent to 14.7:1 air/fuel ratio).
Think of fuel trims as a look up table, as you accelerate the engine you will see different numbers because different loads have their own block on the table, meaning different stored presets for different engine loads.
Short term trims are in direct response to your 02 sensors, TP,IAT, MAF, MAP, etc.. They respond by changing injector pulse width to a certain correction amount until they are finally recognized as a long term correction value and it becomes a Long term fuel trim.
If you are reading live data, you want to compare fuel trims, injector pulse width, and 02 sensor patterns to ensure that they are working together properly.
What else do you want to know? : )
Think of fuel trims as a look up table, as you accelerate the engine you will see different numbers because different loads have their own block on the table, meaning different stored presets for different engine loads.
Short term trims are in direct response to your 02 sensors, TP,IAT, MAF, MAP, etc.. They respond by changing injector pulse width to a certain correction amount until they are finally recognized as a long term correction value and it becomes a Long term fuel trim.
If you are reading live data, you want to compare fuel trims, injector pulse width, and 02 sensor patterns to ensure that they are working together properly.
What else do you want to know? : )
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rdelp
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Jan 27, 2008 12:53 PM
